Showing papers in "Amino Acids in 2008"
TL;DR: Proline (Pro) accumulation is a common physiological response in many plants in response to a wide range of biotic and abiotic stresses as discussed by the authors, and controversy has surrounded the possible role(s) of proline accumulation.
Abstract: Proline (Pro) accumulation is a common physiological response in many plants in response to a wide range of biotic and abiotic stresses. Controversy has surrounded the possible role(s) of proline accumulation. In this review, knowledge on the regulation of Pro metabolism during development and stress, results of genetic manipulation of Pro metabolism and current debate on Pro toxicity in plants are presented.
1,551 citations
TL;DR: Information is summarized about the involvement of polyamines as antioxidants against the potential abiotic stress-derived oxidative damage and other types of abiotic stresses, such as mineral deficiencies, chilling, wounding, heavy metals, UV, ozone and paraquat, where polyamine metabolism is also modified.
Abstract: In this review we will concentrate in the results published the last years regarding the involvement of polyamines in the plant responses to abiotic stresses, most remarkably on salt and drought stress. We will also turn to other types of abiotic stresses, less studied in relation to polyamine metabolism, such as mineral deficiencies, chilling, wounding, heavy metals, UV, ozone and paraquat, where polyamine metabolism is also modified. There is a great amount of data demonstrating that under many types of abiotic stresses, an accumulation of the three main polyamines putrescine, spermidine and spermine does occur. However, there are still many doubts concerning the role that polyamines play in stress tolerance. Several environmental challenges (osmotic stress, salinity, ozone, UV) are shown to induce ADC activity more than ODC. The rise in Put is mainly attributed to the increase in ADC activity as a consequence of the activation of ADC genes and their mRNA levels. On the other hand, free radicals are now accepted as important mediators of tissue injury and cell death. The polycationic nature of polyamines, positively charged at physiological pH, has attracted the attention of researchers and has led to the hypothesis that polyamines could affect physiological systems by binding to anionic sites, such as those associated with nucleic acids and membrane phospholipids. These amines, involved with the control of numerous cellular functions, including free radical scavenger and antioxidant activity, have been found to confer protection from abiotic stresses but their mode of action is not fully understood yet. In this review, we will also summarize information about the involvement of polyamines as antioxidants against the potential abiotic stress-derived oxidative damage.
725 citations
TL;DR: Understanding the physiological role of SVCT1 and SVCT2 may lead to develop new therapeutic strategies to control intracellular vitamin C content or to promote tissue-specific delivery of vitamin C-drug conjugates.
Abstract: Vitamin C is accumulated in mammalian cells by two types of proteins: sodium-ascorbate co-transporters (SVCTs) and hexose transporters (GLUTs); in particular, SVCTs actively import ascorbate, the reduced form of this vitamin. SVCTs are surface glycoproteins encoded by two different genes, very similar in structure. They show distinct tissue distribution and functional characteristics, which indicate different physiological roles. SVCT1 is involved in whole-body homeostasis of vitamin C, while SVCT2 protects metabolically active cells against oxidative stress. Regulation at mRNA or protein level may serve for preferential accumulation of ascorbic acid at sites where it is needed. This review will summarize the present knowledge on structure, function and regulation of the SVCT transporters. Understanding the physiological role of SVCT1 and SVCT2 may lead to develop new therapeutic strategies to control intracellular vitamin C content or to promote tissue-specific delivery of vitamin C-drug conjugates.
311 citations
TL;DR: It is proposed that proline is made available as a stress substrate by the degradation of collagen in the microenvironmental extracellular matrix by matrix metalloproteinases in a manner analogous to autophagy, and this proline-dependent process for bioenergetics from collagen in extacellular matrix can be designated “ecophagy”.
Abstract: The resurgence of interest in tumor metabolism has led investigators to emphasize the metabolism of proline as a “stress substrate” and to suggest this pathway as a potential anti-tumor target. Proline oxidase, a.k.a. proline dehydrogenase (POX/PRODH), catalyzes the first step in proline degradation and uses proline to generate ATP for survival or reactive oxygen species for programmed cell death. POX/PRODH is induced by p53 under genotoxic stress and initiates apoptosis by both mitochondrial and death receptor pathways. Furthermore, POX/PRODH is induced by PPARγ and its pharmacologic ligands, the thiazolidinediones. The anti-tumor effects of PPARγ may be critically dependent on POX/PRODH. In addition, it is upregulated by nutrient stress through the mTOR pathway to maintain ATP levels. We propose that proline is made available as a stress substrate by the degradation of collagen in the microenvironmental extracellular matrix by matrix metalloproteinases. In a manner analogous to autophagy, this proline-dependent process for bioenergetics from collagen in extracellular matrix can be designated “ecophagy”.
228 citations
TL;DR: It is implied by extension that free proline, known to accumulate in plant tissues during abiotic stresses, would contribute to scavenging of surplus free radicals produced under a variety of abiotic pressures.
Abstract: An assessment of the potential of proline to scavenge free radicals was made in a couple of in vitro assay systems, namely graft co-polymerization and autooxidation of pyrogallol. Both these assays are essentially dependent upon free radical mechanisms. Graft co-polymerization involved a ceric (Ce(4+)) ion- or gamma-radiation-induced grafting of methyl acrylate (MA) onto a cellulose backbone. The degree of grafting, measured gravimetrically, was taken as a measure of free radical generation. The gamma-radiation-dependent grafting was far greater than that due to Ce(4+) ions. Inclusion of proline in the assay, irrespective of the initiator used, led to suppression of grafting in a concentration-dependent manner indicating the ability of proline to scavenge free radicals. The gamma-radiation-dependent grafting was also suppressed by hydroquinone and glutathione but not by ascorbate, glycine and spermine. In contrast to graft co-polymerization, proline did not inhibit the autooxidation of pyrogallol, a reaction involving superoxide radical generation. A subset of data constitutes an evidence for the ability of proline to scavenge free radicals in vitro. It is implied by extension that free proline, known to accumulate in plant tissues during abiotic stresses, would contribute to scavenging of surplus free radicals produced under a variety of abiotic stresses.
206 citations
TL;DR: Bioactive peptides derived from β-Lg are currently a point of intensive research, including antihypertensive, antioxidant and antimicrobial activities as well as opioid-like features and ability to decrease the body-cholesterol levels.
Abstract: β-Lactoglobulin (β-Lg) is currently an important source of biologically active peptides. These peptides are inactive within the sequence of the precursor protein, but they can be released by in vivo or in vitro enzymatic proteolysis. Once released, these peptides play important roles in the human health, including antihypertensive, antioxidant and antimicrobial activities as well as opioid-like features and ability to decrease the body-cholesterol levels. Bioactive peptides derived from β-Lg are currently a point of intensive research. Their structure, biological significance and mechanism of action are briefly presented and discussed in this review.
193 citations
TL;DR: Novel findings suggest an important role for proline in conceptus metabolism, growth and development, as well as a potential treatment for intrauterine growth restriction, which is a significant problem in both human medicine and animal agriculture.
Abstract: Although there are published studies of proline biochemistry and nutrition in cultured cells and postnatal animals, little is known about proline metabolism and function in the conceptus (embryo/fetus, associated placental membranes, and fetal fluids). Because of the invasive nature of biochemical research on placental and fetal growth, animal models are often used to test hypotheses of biological importance. Recent evidence from studies with pigs and sheep shows that proline is a major substrate for polyamine synthesis via proline oxidase, ornithine aminotransferase, and ornithine decarboxylase in placentae. Both porcine and ovine placentae have a high capacity for proline catabolism and polyamine production. In addition, allantoic and amniotic fluids contain enzymes to convert proline into ornithine, which is delivered through the circulation to placental tissues. There is exquisite metabolic coordination among integrated pathways that support highest rates of polyamine synthesis and concentrations in placentae during early gestation when placental growth is most rapid. Interestingly, reduced placental and fetal growth are associated with reductions in placental proline transport, proline oxidase activity, and concentrations of polyamines in gestating dams with either naturally occurring or malnutrition-induced growth retardation. Conversely, increasing proline availability in maternal plasma through nutritional or pharmacological modulation in pigs and sheep enhances concentrations of proline and polyamines in placentae and fetal fluids, as well as fetal growth. These novel findings suggest an important role for proline in conceptus metabolism, growth and development, as well as a potential treatment for intrauterine growth restriction, which is a significant problem in both human medicine and animal agriculture.
176 citations
TL;DR: The administration of H2S protected the myocardium from oxidative and ER stress induced by HHcy, which suggests that an endogenous metabolic balance of sulfur-containing amino acids may be a novel strategy for treatment of HHcy.
Abstract: Hyperhomocysteinemia (HHcy) is a critical independent risk factor for cardiovascular diseases. However, to date, no satisfactory strategies to prevent HHcy exist. Since homocysteine (Hcy) and endogenous H2S are both metabolites of sulfur-containing amino acids, we aimed to investigate whether a metabolic product of Hcy and H2S, may antagonize in part the cardiovascular effects of Hcy. In the HHcy rat model injected subcutaneously with Hcy for 3 weeks, H2S levels and the H2S-generating enzyme cystathionine γ lyase (CSE) activity in the myocardium were decreased. The intraperitoneal injection of H2S gas saturation solution significantly reduced plasma total Hcy (tHcy) concentration and decreased lipid peroxidation formation (i.e., lowered manodialdehyde and conjugated diene levels in myocardia and plasma). The activities of myocardial mitochondrial respiratory enzymes succinate dehydrogenase, cytochrome oxidase, and manganese superoxide dismutase, related to reactive oxygen species metabolism, were significantly dysfunctional in HHcy rats. The H2S administration restored the level of enzyme activities and accelerated the scavenging of H2O2 and superoxide anion generated by Hcy in isolated mitochondria. The H2S treatment also inhibited the expression of glucose-regulated protein 78, a marker of endoplasmic reticulum (ER) stress, induced by Hcy in vivo and in vitro. Thus, HHcy impaired the myocardial CSE/H2S pathway, and the administration of H2S protected the myocardium from oxidative and ER stress induced by HHcy, which suggests that an endogenous metabolic balance of sulfur-containing amino acids may be a novel strategy for treatment of HHcy.
169 citations
TL;DR: In conclusion, 10 weeks of resistance training alone did not change M-[Carn], and the aim of this investigation was to investigate if increased M:[Carn] brought about through β-ala supplementation had a positive effect on training responses.
Abstract: Carnosine (Carn) occurs in high concentrations in skeletal muscle is a potent physico-chemical buffer of H+ over the physiological range. Recent research has demonstrated that 6.4 g.day−1 of β-alanine (β-ala) can significantly increase skeletal muscle Carn concentrations (M-[Carn]) whilst the resultant change in buffering capacity has been shown to be paralleled by significant improvements in anaerobic and aerobic measures of exercise performance. Muscle carnosine increase has also been linked to increased work done during resistance training. Prior research has suggested that strength training may also increase M-[Carn] although this is disputed by other studies. The aim of this investigation is to assess the effect of 10 weeks resistance training on M-[Carn], and, secondly, to investigate if increased M-[Carn] brought about through β-ala supplementation had a positive effect on training responses. Twenty-six Vietnamese sports science students completed the study. The subjects completed a 10-week resistance-training program whilst consuming 6.4 g.day−1 of β-ala (β-ALG) or a matched dose of a placebo (PLG). Subjects were assessed prior to and after training for whole body strength, isokinetic force production, muscular endurance, body composition. β-Alanine supplemented subjects increased M-[Carn] by 12.81 ± 7.97 mmol.kg−1 dry muscle whilst there was no change in PLG subjects. There was no significant effect of β-ala supplementation on any of the exercise parameters measured, mass or % body fat. In conclusion, 10 weeks of resistance training alone did not change M-[Carn].
164 citations
TL;DR: The mechanism of detoxification of glyoxal and methylglyoxal by the Glyoxalase system is described and also the possibility to eliminate glycated proteins by deglycation enzymes is described.
Abstract: Advanced glycation end-products (AGEs) are formed from the so-called Amadori products by rearrangement followed by other reactions giving rise to compounds bound irreversibly. The structure of some of them is shown and the mechanism of formation is described. Several AGE binding molecules (Receptors for AGE, RAGE) are known and it is thought that many of the effects caused by AGEs are mediated by RAGE. Some of these were shown to be toxic, and called TAGE. The mechanism of detoxification of glyoxal and methylglyoxal by the glyoxalase system is described and also the possibility to eliminate glycated proteins by deglycation enzymes. Compounds able to inhibit AGEs formation are also taken into consideration.
163 citations
TL;DR: Some generalized features of amino acid composition found in thermophilic proteins, including an increase in residue hydrophobicity, a decrease in uncharged polar residues, an increases in charged residues, a increase in aromatic residues, certain amino acid coupling patterns and amino acid preferences for thermophile proteins are presented.
Abstract: Thermophilic proteins show substantially higher intrinsic thermal stability than their mesophilic counterparts. Amino acid composition is believed to alter the intrinsic stability of proteins. Several investigations and mutagenesis experiment have been carried out to understand the amino acid composition for the thermostability of proteins. This review presents some generalized features of amino acid composition found in thermophilic proteins, including an increase in residue hydrophobicity, a decrease in uncharged polar residues, an increase in charged residues, an increase in aromatic residues, certain amino acid coupling patterns and amino acid preferences for thermophilic proteins. The differences of amino acids composition between thermophilic and mesophilic proteins are related to some properties of amino acids. These features provide guidelines for engineering mesophilic protein to thermophilic protein.
TL;DR: This work proposes a submitochondria localizer whose feature extraction method is based on the Chou’s pseudo-amino acid composition, and proposes a very few parameterized method, named ALL-Loc, where all the “ original” features are used to train a linear support vector machine.
Abstract: Given a protein that is localized in the mitochondria it is very important to know the submitochondria localization of that protein to understand its function. In this work, we propose a submitochondria localizer whose feature extraction method is based on the Chou's pseudo-amino acid composition. The pseudo-amino acid based features are obtained by combining pseudo-amino acid compositions with hundreds of amino-acid indices and amino-acid substitution matrices, then from this huge set of features a small set of 15 "artificial" features is created. The feature creation is performed by genetic programming combining one or more "original" features by means of some mathematical operators. Finally, the set of combined features are used to train a radial basis function support vector machine. This method is named GP-Loc. Moreover, we also propose a very few parameterized method, named ALL-Loc, where all the "original" features are used to train a linear support vector machine. The overall prediction accuracy obtained by GP-Loc is 89% when the jackknife cross-validation is used, this result outperforms the performance obtained in the literature (85.2%) using the same dataset. While the overall prediction accuracy obtained by ALL-Loc is 83.9%.
TL;DR: This study proposes a method based on alone the primary sequences of proteins to predict the DNA-binding proteins and suggests that it can efficiently predict the novel DNA- binding proteins only using thePrimary sequences.
Abstract: DNA-binding proteins play a pivotal role in gene regulation. It is vitally important to develop an automated and efficient method for timely identification of novel DNA-binding proteins. In this study, we proposed a method based on alone the primary sequences of proteins to predict the DNA-binding proteins. DNA-binding proteins were encoded by autocross-covariance transform, pseudo-amino acid composition, dipeptide composition, respectively and also the different combinations of the three encoded methods; further, these feature matrices were applied to support vector machine classifiers to predict the DNA-binding proteins. All modules were trained and validated by the jackknife cross-validation test. Through comparing the performance of these substituted modules, the best result was obtained from pseudo-amino acid composition with the overall accuracy of 96.6% and the sensitivity of 90.7%. The results suggest that it can efficiently predict the novel DNA-binding proteins only using the primary sequences.
TL;DR: It is reported here that pre-treatment of cerebellar granule cells with taurine significantly counteracted glutamate excitotoxicity and the overall mitochondrial function was increased in the presence of taurines, as assessed by rhodamine accumulation into mitochondria and total cellular ATP levels.
Abstract: We have determined the role of mitochondria in the sequestration of calcium after stimulation of cerebellar granule cells with glutamate. In addition we have evaluated the neuroprotective role of taurine in excitotoxic cell death. Mitochondrial inhibitors were used to determine the calcium buffering capacity of mitochondria, as well as how taurine regulates the ability of mitochondria to buffer intracellular calcium during glutamate depolarization and excitotoxicity. We report here that pre-treatment of cerebellar granule cells with taurine (1 mM, 24 h) significantly counteracted glutamate excitotoxicity. The neuroprotective role of taurine was mediated through regulation of cytoplasmic free calcium ([Ca(2+)]( i )), and intra-mitochondrial calcium homeostasis, as determined by fluo-3 and (45)Ca(2+)-uptake. Furthermore, the overall mitochondrial function was increased in the presence of taurine, as assessed by rhodamine accumulation into mitochondria and total cellular ATP levels. We specifically tested the hypothesis that taurine reduces glutamate excitotoxicity through both the enhancement of mitochondrial function and the regulation of intracellular (cytoplasmic and intra-mitochondrial) calcium homeostasis. The role of taurine in modulating mitochondrial calcium homeostasis could be of particular importance under pathological conditions that are characterized by excessive calcium overloads. Taurine may serve as an endogenous neuroprotective molecule against brain insults.
TL;DR: The Streptococcus salivarius subsp.
Abstract: γ-Aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system, has several well-known physiological functions and has been applied to the production of many drugs and functional foods. The technology of GABA production via submerged fermentation by Streptococcus salivarius subsp. thermophilus Y2 was investigated in this paper. It indicated that the GABA production was related to the biochemical characteristics of glutamate decarboxylase (GAD) of S. salivarius subsp. thermophilus Y2. After 24 h of fermentation at 37 °C, which is the suitable culture conditions for GAD-production, then the culture condition were adjusted to the optimal temperature (40 °C) and pH (4.5) for the GAD reaction activity in biotransformation of cells and pyridoxal 5′-phosphate (0.02 mmol/l) were added to the broth at the 48 h, the GABA production was increased up to 1.76-fold, reaching 7984.75 ± 293.33 mg/l. The strain shows great potential use as a starter for GABA-containing yoghurt, cheese and other functional fermented food productions.
TL;DR: Evidence is provided for prolidase-dependent transcriptional regulation of collagen biosynthesis at the level of NF-kB, known inhibitor of type I collagen gene expression and the mechanism was found at both transcriptional and post-transcriptional levels.
Abstract: Prolidase [EC.3.4.13.9] is a cytosolic imidodipeptidase, which specifically splits imidodipeptides with C-terminal proline or hydroxyproline. The enzyme plays an important role in the recycling of proline from imidodipeptides (mostly derived from degradation products of collagen) for resynthesis of collagen and other proline-containing proteins. The enzyme activity is up-regulated by β1-integrin receptor stimulation. The increase in the enzyme activity is due to its phosphorylation on serine/threonine residues. Collagen is not only structural component of extracellular matrix. It has been recognized as a ligand for integrin receptors, which play an important role in signaling that regulate ion transport, lipid metabolism, kinase activation and gene expression. Therefore, changes in the quantity, structure and distribution of collagens in tissues may affect cell signaling, metabolism and function. Several line of evidence suggests that prolidase activity may be a step-limiting factor in the regulation of collagen biosynthesis. It has been shown in different physiologic and pathologic conditions. It is of great importance during wound healing, inflammation, aging, tissue fibrosis and possibly skeletal abnormalities seen in Osteogenesis Imperfecta. The mechanism of prolidase-dependent regulation of collagen biosynthesis was found at both transcriptional and post-transcriptional levels. In this study, we provide evidence for prolidase-dependent transcriptional regulation of collagen biosynthesis. The mechanism was found at the level of NF-kB, known inhibitor of type I collagen gene expression. Modulation of integrin-dependent signaling by stimulatory (i.e. thrombin) or inhibitory (i.e. echistatin) β1-integrin ligands or by nitric oxide donors (i.e. DETA/NO) affect prolidase at post-transcriptional level. All those factors may represent novel approach to pharmacotherapy of connective tissue disorders.
TL;DR: Three-dimensional structural information that is currently available for proline catabolic enzymes is reviewed and some of the functional insights provided by analyses of these structures are discussed, including substrate recognition, catalytic mechanism, biochemical basis of inherited prolineCatabolic disorders and DNA recognition by proline utilization A.
Abstract: The proline catabolic enzymes proline dehydrogenase and Δ1-pyrroline-5-carboxylate dehydrogenase catalyze the 4-electron oxidation of proline to glutamate. These enzymes play important roles in cellular redox control, superoxide generation, apoptosis and cancer. In some bacteria, the two enzymes are fused into the bifunctional enzyme, proline utilization A. Here we review the three-dimensional structural information that is currently available for proline catabolic enzymes. Crystal structures have been determined for bacterial monofunctional proline dehydrogenase and Δ1-pyrroline-5-carboxylate dehydrogenase, as well as the proline dehydrogenase and DNA-binding domains of proline utilization A. Some of the functional insights provided by analyses of these structures are discussed, including substrate recognition, catalytic mechanism, biochemical basis of inherited proline catabolic disorders and DNA recognition by proline utilization A.
TL;DR: S-adenosylmethionine is involved in many processes, mainly methylation, polyamine synthesis and radical-based catalysis, and is synthesised through the catalysis of differently regulated enzyme forms.
Abstract: S-adenosylmethionine is involved in many processes, mainly methylation, polyamine synthesis and radical-based catalysis. It is synthesised through the catalysis of differently regulated enzyme forms. When it is used, the compounds formed are reutilized in different ways: in case of methylation, its end product is homocysteine, which can be remethylated to methionine, give rise to cysteine in the so-called transsulphuration pathway, or be released; in the case of polyamine synthesis, the methylthioadenosine formed is cleaved and gives rise to compounds which can be reutilized; during radical-based catalysis, 5-deoxyadenosine is formed and this, too, is cleaved and reutilized.
TL;DR: Based on the concept of Chou’s pseudo-amino acid composition, a hybridization predictor was developed for identifying uncharacterized proteins among the following 12 subcellular localizations, suggesting that the current approach is quite promising, and may become a useful high-throughput tool in the relevant areas.
Abstract: The rapidly increasing number of sequence entering into the genome databank has called for the need for developing automated methods to analyze them. Information on the subcellular localization of new found protein sequences is important for helping to reveal their functions in time and conducting the study of system biology at the cellular level. Based on the concept of Chou's pseudo-amino acid composition, a series of useful information and techniques, such as residue conservation scores, von Neumann entropies, multi-scale energy, and weighted auto-correlation function were utilized to generate the pseudo-amino acid components for representing the protein samples. Based on such an infrastructure, a hybridization predictor was developed for identifying uncharacterized proteins among the following 12 subcellular localizations: chloroplast, cytoplasm, cytoskeleton, endoplasmic reticulum, extracell, Golgi apparatus, lysosome, mitochondria, nucleus, peroxisome, plasma membrane, and vacuole. Compared with the results reported by the previous investigators, higher success rates were obtained, suggesting that the current approach is quite promising, and may become a useful high-throughput tool in the relevant areas.
TL;DR: Prolines, as determinants of substrate specificity and susceptibility, also play a role in degradation of collagen by collagenolytic matrix metalloproteinases (MMPs).
Abstract: Collagens are among proteins that undergo several post-translational modifications, such as prolyl hydroxylation, that occur during elongation of the nascent chains in the endoplasmic reticulum. The major structural collagens, types I, II and III, have large, uninterrupted triple helices, comprising three polyproline II-like chains supercoiled around a common axis. The structure has a requirement for glycine, as every third residue, and is stabilized by the high content of proline and 4-hydroxyproline residues. Action of prolyl hydroxylases is critical. Spontaneous or targeted genetic defects in prolyl hydroxylases can be lethal or result in severe osteogenesis imperfecta. Prolines, as determinants of substrate specificity and susceptibility, also play a role in degradation of collagen by collagenolytic matrix metalloproteinases (MMPs). Targeted mutations in mice in the collagenase cleavage domain have profound effects on collagen turnover and the function of connective tissues. Prolines are thus critical determinants of collagen structure and function.
TL;DR: Recombinant human prolidase was produced in prokaryotic and eukaryotic hosts with biochemical properties similar to the endogenous enzyme and represents a valid tool both to better understand the structure and biological function of the enzyme and to develop an enzyme replacement therapy for the prolid enzyme deficiency (PD).
Abstract: Here we summarized what is known at the present about function, structure and effect of mutations in the human prolidase. Among the peptidases, prolidase is the only metalloenzyme that cleaves the iminodipeptides containing a proline or hydroxyproline residue at the C-terminal end. It is relevant in the latest stage of protein catabolism, particularly of those molecules rich in imino acids such as collagens, thus being involved in matrix remodelling. Beside its intracellular functions, prolidase has an antitoxic effect against some organophosphorus molecules, can be used in dietary industry as bitterness reducing agent and recently has been used as target enzyme for specific melanoma prodrug activation. Recombinant human prolidase was produced in prokaryotic and eukaryotic hosts with biochemical properties similar to the endogenous enzyme and represents a valid tool both to better understand the structure and biological function of the enzyme and to develop an enzyme replacement therapy for the prolidase deficiency (PD). Prolidase deficiency is a rare recessive disorder caused by mutations in the prolidase gene and characterized by severe skin lesions. Single amino acid substitutions, exon splicing, deletions and a duplication were described as causative for the disease and are mainly located at highly conserved amino acids in the sequence of prolidase from different species. The pathophysiology of PD is still poorly understood; we offer here a review of the molecular mechanisms so far hypothesized.
TL;DR: This simple, rapid and elegant method will be valuable to the amino acid analyst and researcher, as it can save much manpower time and meet urgent emergency requests and the demands of a high-throughput laboratory.
Abstract: The Phenomenex EZ:faast™ amino acid analysis kit is available for gas (GC) or liquid (LC) chromatographic analysis of amino acids (AA) using mass spectrometry (MS) and other GC detectors. We used it for rapid GC determination of plasma tryptophan, its brain uptake competitors (Val, Leu, Ile, Phe and Tyr) and many other amino acids. Based on solid-phase extraction, this fast method enables one person to process two plasma samples in 8–10 min and six samples in ∼15 min up to GC injection and a 7-min GC run per plasma sample. Using a Perkin-Elmer Clarus 500 GC, a Total Chrome software, a flame-ionisation detector (FID) and norvaline as internal standard, we used this method to analyse ∼1,000 plasma samples from normal subjects undergoing acute tryptophan depletion and loading tests. The limit of detection for most amino acids is 1 nmol/ml (1 μM) and in many cases less. With manual injection, coefficients of variation for the above six amino acids were 1.5–6.2% (intra-assay) and 3.8–9.7% (inter-assay). This simple, rapid and elegant method will be valuable to the amino acid analyst and researcher, as it can save much manpower time and meet urgent emergency requests and the demands of a high-throughput laboratory.
TL;DR: This review will focus on the regulation of TORC1 in mammalian cells in the context of amino acid sensing/regulation and intracellular ATP homeostasis, but will also include comparisons among other organisms.
Abstract: The TOR (Target of Rapamycin) protein kinase pathway plays a central role in sensing and responding to nutrients, stress, and intracellular energy state. TOR complex 1 (TORC1) is comprised of TOR, Raptor, and Lst8 and its activity is sensitive to inhibition by the macrolide antibiotic rapamycin. TORC1 regulates protein synthesis, ribosome biogenesis, autophagy, and ultimately cell growth through the phosphorylation of S6 K, 4E-BP, and other substrates. As TORC1 activity is positively or negatively modulated in response to upstream regulators, cellular growth rate is, respectively, enhanced or suppressed. A separate multiprotein TOR complex, TORC2, is insensitive to direct inhibition by rapamycin and does not regulate growth patterns directly; TORC2 can, however, impact certain aspects of TORC1 signaling and cell survival. TOR signaling is an ancient pathway, conserved among the yeasts, Dictyostelium, C. elegans, Drosophila, mammals, and Arabidopsis. This review will focus on the regulation of TORC1 in mammalian cells in the context of amino acid sensing/regulation and intracellular ATP homeostasis, but will also include comparisons among other organisms.
TL;DR: Creatine supplementation before a long distance triathlon competition may reduce the inflammatory response induced by this form of strenuous of exercise.
Abstract: Objective. The effect of creatine supplementation upon plasma levels of pro-inflammatory cytokines: Interleukin (IL) 1β and IL-6, Tumor Necrosis Factor α (TNFα), and Interferon α (INFα) and Prostaglandin E2 (PGE2) after a half-ironman competition were investigated.
TL;DR: Using a quantitative proteomic approach, it was showed that P5CS.long is upregulated by p53 in p53-induced apoptosis in DLD-1 colorectal cancer cells and P5 CS.short expression is regulated by hormones and factors of alternative splicing in cells isolated from model animals.
Abstract: Mammalian Delta(1)-pyrroline-5-carboxylate synthase (P5CS) is a bifunctional ATP- and NAD(P)H-dependent mitochondrial enzyme that catalyzes the coupled phosphorylation and reduction-conversion of L: -glutamate to P5C, a pivotal step in the biosynthesis of L: -proline, L: -ornithine and L: -arginine. Previously, we reported cloning and characterization of two P5CS transcript variants generated by exon sliding that encode two protein isoforms differing only by a two amino acid-insert at the N-terminus of the gamma-glutamyl kinase active site. The short form (P5CS.short) is highly expressed in the gut and is inhibited by ornithine. In contrast, the long form (P5CS.long) is expressed ubiquitously and is insensitive to ornithine. Interestingly, we found that all the established human cell lines we have studied expressed P5CS.long but not P5CS.short. In addition, expression of P5CS.long can be modulated by hormones: downregulation by hydrocortisone and dexamethasone and upregulation by estradiol, for example. Using a quantitative proteomic approach, we showed that P5CS.long is upregulated by p53 in p53-induced apoptosis in DLD-1 colorectal cancer cells. Functional genomic analysis confirmed that there are two p53-binding consensus sequences in the promoter region and in the intron 1 of the human P5CS gene. Interestingly, overexpression of P5CS by adenoviruses harboring P5CS.long or P5CS.short in various cell types has no effect on cell growth or survival. It would be of importance to further investigate the role of P5CS as a p53 downstream effector and how P5CS.short expression is regulated by hormones and factors of alternative splicing in cells isolated from model animals.
TL;DR: It is concluded that APP overeexpression seems to be absent during the development of DS brain up to 18–19 weeks of gestational age, however, its overexpression in adult DS brain could lead to disturbance of normal function of APP contributing to neurodegeneration.
Abstract: Down syndrome (DS) is the most common human chromosomal abnormality caused by an extra copy of chromosome 21. The phenotype of DS is thought to result from overexpression of a gene or genes located on the triplicated chromosome or chromosome region. Several reports have shown that the neuropathology of DS comprises developmental abnormalities and Alzheimer-like lesions such as senile plaques. A key component of senile plaques is amyloid beta-peptide which is generated from the amyloid precursor protein (APP) by sequential action of beta-secretases (BACE1 and BACE2) and gamma-secretase. While BACE1 maps to chromosome 11, APP and BACE2 are located on chromosome 21. To challenge the gene dosage effect and gain insight into the expressional relation between beta-secretases and APP in DS brain, we evaluated protein expression levels of BACE1, BACE2 and APP in fetal and adult DS brain compared to controls. In fetal brain, protein expression levels of BACE2 and APP were comparable between DS and controls. BACE1 was increased, but did not reach statistical significance. In adult brain, BACE1 and BACE2 were comparable between DS and controls, but APP was significantly increased. We conclude that APP overexpression seems to be absent during the development of DS brain up to 18-19 weeks of gestational age. However, its overexpression in adult DS brain could lead to disturbance of normal function of APP contributing to neurodegeneration. Comparable expression of BACE1 and BACE2 speaks against the hypothesis that increased beta-secretase results in (or even underlies) increased production of amyloidogenic A beta fragments. Furthermore, current data indicate that the DS phenotype cannot be fully explained by simple gene dosage effect.
TL;DR: It is indicated that while taurine is essential for growth of JF, it is not essential for the growth of CC.
Abstract: This study was conducted to investigate taurine deficiency and the ability of taurine biosynthesis in both juvenile Japanese flounder (JF) and juvenile common carp (CC) in vivo using low taurine level diets. Three different taurine level diets were prepared by the supplementation of taurine to the basal composition (JF – 0, 0.5 and 1.5% in JF; CC – 0, 1, 3% in CC). The final average body weight and feed efficiency of JF fed the JF – 1.5% was significantly higher than those of fish fed on the JF – 0%. On the other hand, no significant difference was observed in CC fed with CC – 0, 1, and 3% diets. The taurine retention rate was negative in the case of JF-fed with the taurine-free supplement (JF – 0%). On the other hand, the taurine retention rate was about 280% in the case of CC-fed with the taurine-free supplement (CC – 0%). These findings indicate that while taurine is essential for growth of JF, it is not essential for the growth of CC.
TL;DR: It is reported that kynurenic acid is present in the lumen of rat small intestine in micromolar concentration sufficient to affect the GPR35 receptor, and it is suggested that kysine may modulate gastrointestinal function and integrity.
Abstract: Kynurenic acid is an antagonist of glutamate and alpha-7 nicotinic acetylcholine receptors and an agonist of the g-protein-coupled receptor GPR35, which is predominantly expressed in immune and gastrointestinal tissues. In this study, we report that kynurenic acid is present in the lumen of rat small intestine in micromolar concentration sufficient to affect the GPR35 receptor. Moreover, we show that kynurenic acid can be produced by Escherichia coli. We suggest that kynurenic acid may modulate gastrointestinal function and integrity.
TL;DR: This assumption that Oxidative stress due to immune activation and inflammation may destroy cofactor 5,6,7,8-tetrahydrobiopterin and impair PAH activity is supported by the correlation found between higher neopterin concentrations and higher phenylalanine to tyrosine ratio, which estimates efficacy of PAH.
Abstract: Increased blood concentrations of phenylalanine in patients with trauma and sepsis are common but unexplained. We examined the potential relationship between serum concentrations of phenylalanine and the immune activation marker neopterin in 84 specimens of 18 patients (14 males and 4 females) post-trauma during 12-14 days of follow up. Compared to healthy controls, average phenylalanine and neopterin concentrations were elevated in patients, and there existed a positive correlation between concentrations of the two analytes (r (s) = 0.375, p < 0.001). No such association existed between neopterin and tyrosine concentrations (r (s) = -0.018), but neopterin concentrations correlated to the phenylalanine to tyrosine ratio (r (s) = 0.328, p = 0.001). Increased phenylalanine implies insufficient conversion by phenylalanine (4)-hydroxylase (PAH). Oxidative stress due to immune activation and inflammation may destroy cofactor 5,6,7,8-tetrahydrobiopterin and impair PAH activity. This assumption is further supported by the correlation found between higher neopterin concentrations and higher phenylalanine to tyrosine ratio, which estimates efficacy of PAH.
TL;DR: In this review, the structural properties of a number of myelin-specific proteins are described and their roles in neurological diseases and peripheral neuropathies are investigated.
Abstract: The myelin sheath is an insulating membrane layer surrounding myelinated axons in vertebrates, which is formed when the plasma membrane of an oligodendrocyte or a Schwann cell wraps itself around the axon. A large fraction of the total protein in this membrane layer is comprised of only a small number of individual proteins, which have certain intriguing structural properties. The myelin proteins are implicated in a number of neurological diseases, including, for example, autoimmune diseases and peripheral neuropathies. In this review, the structural properties of a number of myelin-specific proteins are described.