Showing papers on "Methylglyoxal published in 1997"
TL;DR: Levels of CML and CEL are proposed to provide an index of glyoxal and methylglyoxal concentrations in tissues, alterations in glutathione homoeostasis and dicarbonyl metabolism in disease, and sources of advanced glycation end-products in tissue proteins in aging and disease.
Abstract: Advanced glycation end-products and glycoxidation products, such as Nepsilon-(carboxymethyl)lysine (CML) and pentosidine, accumulate in long-lived tissue proteins with age and are implicated in the aging of tissue proteins and in the development of pathology in diabetes, atherosclerosis and other diseases. In this paper we describe a new advanced glycation end-product, Nepsilon-(carboxyethyl)lysine (CEL), which is formed during the reaction of methylglyoxal with lysine residues in model compounds and in the proteins RNase and collagen. CEL was also detected in human lens proteins at a concentration similar to that of CML, and increased with age in parallel with the concentration of CML. Although CEL was formed in highest yields during the reaction of methylglyoxal and triose phosphates with lysine and protein, it was also formed in reactions of pentoses, ascorbate and other sugars with lysine and RNase. We propose that levels of CML and CEL and their ratio to one another in tissue proteins and in urine will provide an index of glyoxal and methylglyoxal concentrations in tissues, alterations in glutathione homoeostasis and dicarbonyl metabolism in disease, and sources of advanced glycation end-products in tissue proteins in aging and disease.
606 citations
TL;DR: It is indicated that argpyrimidine is synthesized through an intermediate 3-hydroxypentane-2,4-dione and provide a chemical basis for fluorescence in proteins modified by methylglyoxal, suggesting that it is a major product in such modified proteins.
270 citations
TL;DR: Comparison of glyoxalase I with other known structures shows the enzyme to belong to a new structural family which includes the Fe2+‐dependent dihydroxybiphenyl dioxygenase and the bleomycin resistance protein, which appears to allow members to form with or without domain swapping.
Abstract: The zinc metalloenzyme glyoxalase I catalyses the glutathione-dependent inactivation of toxic methylglyoxal. The structure of the dimeric human enzyme in complex with S-benzyl-glutathione has been ...
221 citations
TL;DR: The ability of 4-hydroxynonenal at low concentrations to inactivate glutathione reductase, a central antioxidant enzyme, suggests that oxidative degradation of unsaturated lipids may initiate a positive feedback loop that enhances the potential for oxidative damage.
147 citations
TL;DR: The results support the hypothesis that increased SSAO-mediated deamination may be involved in structural modification of proteins and contribute to advanced glycation in diabetes.
Abstract: Aminoguanidine, a nucleophilic hydrazine, has been shown to be capable of blocking the formation of advanced glycation end products. It reduces the development of atherosclerotic plaques and prevents experimental diabetic nephropathy. We have found that aminoguanidine is also quite potent at inhibiting semicarbazide-sensitive amine oxidase (SSAO) both in vitro and in vivo. The inhibition is irreversible. This enzyme catalyses the deamination of methylamine and aminoacetone, which leads to the production of cytotoxic formaldehyde and methylglyoxal, respectively. Serum SSAO activity was reported to be increased in diabetic patients and positively correlated with the amount of plasma glycated haemoglobin. Increased SSAO has also been demonstrated in diabetic animal models. Urinary excretion of methylamine is substantially increased in the rats following acute or chronic treatment with aminoguanidine. Urinary methylamine levels were substantially increased in streptozotocin (STZ)-induced diabetic rats following administration of aminoguanidine. The non-hydrazine SSAO inhibitor (E)-2-(4-fluorophenethyl)-3-fluoroallylamine hydrochloride (MDL-72974A) has been shown to reduce urinary excretion of lactate dehydrogenase (an indicator of nephropathy) in STZ-induced diabetic rats. Formaldehyde not only induces protein crosslinking, but also enhances the advanced glycation of proteins in vitro. The results support the hypothesis that increased SSAO-mediated deamination may be involved in structural modification of proteins and contribute to advanced glycation in diabetes. The clinical implications for the use of aminoguanidine to prevent glycoxidation have been discussed.
130 citations
TL;DR: The induction of HB-EGF by MG and 3-DG, as well as the concomitant increment of intracellular peroxides, may trigger atherogenesis during diabetes.
107 citations
TL;DR: It is concluded that methylglyoxal inhibits glycolysis and the electron flow through mitochondrial complex I of leukaemic leucocytes, strikingly similar to previous studies on mitochondrial respiration, glycoleysis and ATP levels in Ehrlich ascites carcinoma cells.
Abstract: The effect of methylglyoxal on the oxygen consumption of mitochondria of both normal and leukaemic leucocytes was tested by using different respiratory substrates and complex specific artificial electron donors and inhibitors. The results indicate that methylglyoxal strongly inhibits mitochondrial respiration in leukaemic leucocytes, whereas, at a much higher concentration, methylglyoxal fails to inhibit mitochondrial respiration in normal leucocytes. Methylglyoxal strongly inhibits ADP-stimulated alpha-oxoglutarate and malate plus NAD+-dependent respiration, whereas, at a higher concentration, methylglyoxal fails to inhibit succinate and alpha-glycerophosphate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinone and cannot inhibit oxygen consumption when the N,N,N', N'-tetramethyl-p-phenylenediamine by-pass is used. NADH oxidation by sub-mitochondrial particles of leukaemic leucocytes is also inhibited by methylglyoxal. Lactaldehyde, a catabolite of methylglyoxal, can exert a protective effect on the inhibition of leukaemic leucocyte mitochondrial respiration by methylglyoxal. Methylglyoxal also inhibits l-lactic acid formation by intact leukaemic leucocytes and critically reduces the ATP level of these cells, whereas methylglyoxal has no effect on normal leucocytes. We conclude that methylglyoxal inhibits glycolysis and the electron flow through mitochondrial complex I of leukaemic leucocytes. This is strikingly similar to our previous studies on mitochondrial respiration, glycolysis and ATP levels in Ehrlich ascites carcinoma cells [Ray, Dutta, Halder and Ray (1994) Biochem. J. 303, 69-72; Halder, Ray and Ray (1993) Int. J. Cancer 54, 443-449], which strongly suggests that the inhibition of electron flow through complex I of the mitochondrial respiratory chain and inhibition of glycolysis by methylglyoxal may be common characteristics of all malignant cells.
103 citations
TL;DR: The irreversible modification ofprotein by methylglyoxal is a potent signal for the degradation of proteins by monocytic cells in which the arginine derivative, Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine, is the receptor recognition factor.
102 citations
TL;DR: The immunohistochemical analysis revealed that atherosclerotic lesions of human aorta contained 5‐methylimidazolone derivatives whose distributions were identical to those of advanced glycation end products (AGEs) detected by the anti‐AGE antibody.
97 citations
TL;DR: Southern blot and sequence analyses indicate that glyoxalase II proteins are encoded by at least two multigene families in Arabidopsis and two isozymes that are differentially expressed suggests that they may play different roles in the cell.
Abstract: Glyoxalase II is part of the glutathione-dependent glyoxalase detoxification system. In addition to its role in the detoxification of cytotoxic 2-oxo-aldehydes, specifically methylglyoxal, it has been suggested that the glyoxalase system may also play a role in controlling cell differentiation and proliferation. During the analysis of a T-DNA-tagged mutant of Arabidopsis we identified the gene for a glyoxalase II isozyme (GLY1) that appears to be mitochondrially localized. The cDNA encoding a glyoxalase II cytoplasmic isozyme (GLY2) was also isolated and characterized. Southern blot and sequence analyses indicate that glyoxalase II proteins are encoded by at least two multigene families in Arabidopsis. Escherichia coli cells expressing either GLY1 or GLY2 exhibit increased glyoxalase II activity, confirming that they do, in fact, encode glyoxalase II proteins. Northern analysis shows that the two genes are differentially expressed. Transcripts for the mitochondrial isozyme are most abundant in roots, while those for the cytoplasmic isozyme are highest in flower buds. The identification of glyoxalase II isozymes that are differentially expressed suggests that they may play different roles in the cell.
87 citations
TL;DR: It is likely that methylglyoxal undergoes a redox cycle and generates the free radicals which in turn lower the antioxidant status in animals, and the increased levels of lipid peroxidation provide support for the involvement of free radical processes in the detrimental effects of methyl glyoxal.
TL;DR: In this article, two genes coding for the glyoxalase II enzyme from Saccharomyces cerevisiae were isolated and characterized, and the amino acid sequences of the deduced proteins are 59.1% identical.
TL;DR: Similar induction of the synthesis and secretion of TNF-alpha and chemotaxis by monocytes in response to MGmin-HSA in vivo may contribute to atherosclerosis in macro- and micro-angiopathy, particularly in the development of chronic clinical complications of diabetes mellitus.
TL;DR: In this paper, heat induced formation of methylglyoxal (MG) was examined in the caramelization and Maillard reaction and showed that MG concentration was higher in the presence of water than in the absence of water.
01 Jan 1997
TL;DR: Sotolone was found to occur predominantly in the (5s) enantiomeric form (95%) and to have a 6I3CpD value of -19.7%0 as mentioned in this paper.
Abstract: 3-Hydroxy-4,5-dimethyl-2(5H)-fbranone (sotolone) was established as the character impact flavor compound of fenugreek on the basis of gas chromatography-olfactometry. Sotolone was found to occur predominantly in the (5s) enantiomeric form (95%) and to have a 6I3CpD= value of -19.7%0. About 2-25 ppm sotolone were determined in fenugreek of different origins using the isotope dilution assay technique. Sotolone was generated in model systems by thermally induced oxidative deamination of 4-hydroxy-L-isoleucine (HIL) using different carbonyl compounds. Up to 24 mol% yields were obtained by boiling HIL and methylglyoxal as reactive a-dicarbonyl at pH 5 for 10 h. Strecker degradation of HIL was found to be a competitive reaction resulting in the formation of 3 -hydroxy-2-methylbutanal. The lactone of HIL, 3 -amino-4,5-dimethyl-3,4-dihydro-2(5H)-furanone, was found to be a better precursor of sotolone. It generated about 36 mol% sotolone in the presence of methylglyoxal.
TL;DR: The results show that Met-157 has no direct role in catalysis, but is rather involved in forming the substrate-binding site of human glyoxalase I, and the high activity of the glutamine mutant suggests that a structurally equivalent glutamine residue in the N-terminal half of Saccharomyces cerevisiae glyoxals I may be part of a catalytically competent active site.
Abstract: Met-157 in the active site of human glyoxalase I was changed by site-directed mutagenesis into alanine, glutamine or histidine in order to evaluate its possible role in catalysis. The glyoxalase I mutants were expressed in Escherichia coli and purified on an S-hexylglutathione affinity gel. The physicochemical properties of the mutant proteins were similar to those of the wild-type enzyme. The glutamine mutant exhibited the same high specific activity as wild-type glyoxalase I, whereas the alanine and histidine mutants had approx. 20% of wild-type activity. The kcat/Km values of the mutant glyoxalase I determined with the hemithioacetal adduct of glutathione and methylglyoxal were reduced to between 10 and 40% of the wild-type value. This reduction was due to lower kcat values for the alanine and histidine mutants and a twofold increase in the Km value for the glutamine mutant. With the hemithioacetal of glutathione and phenylglyoxal, the kinetic parameters of the mutants were also of the same magnitude as those of wild-type glyoxalase I. Studies with the competitive inhibitors S-hexyl- and S-benzyl-glutathione revealed that the affinity was reduced to 7-11% of the wild-type affinity for the glutamine and alanine mutants and to 30-40% for the histidine mutant, as measured by a comparison of Ki values. The results show that Met-157 has no direct role in catalysis, but is rather involved in forming the substrate-binding site of human glyoxalase I. The high activity of the glutamine mutant suggests that a structurally equivalent glutamine residue in the N-terminal half of Saccharomyces cerevisiae glyoxalase I may be part of a catalytically competent active site.
TL;DR: These studies indicate that the inactivating effect of methylglyoxal on GA3PD specifically of the malignant cells may be a common feature of all the malign cells, and this phenomenon can be used as a simple and rapid device for the detection of malignancy.
Abstract: The effect of methylglyoxal on the activity of glyceraldehyde-3-phosphate dehydrogenase (GA3PD) of several normal human tissues and benign and malignant tumors has been tested. Methylglyoxal inactivated GA3PD of all the malignant cells (47 samples) and the degree of inactivation was in the range of 25-90%, but it had no inhibitory effect on this enzyme from several normal cells (24 samples) and benign tumors (13 samples). When the effect of methylglyoxal on other two dehydrogenases namely glucose 6-phosphate dehydrogenase (G6PD) and L-lactic dehydrogenase (LDH) of similar cells was tested as controls it has been observed that methylglyoxal has some inactivating effect on G6PD of all the normal, benign and malignant samples tested, whereas, LDH remained completely unaffected. These studies indicate that the inactivating effect of methylglyoxal on GA3PD specifically of the malignant cells may be a common feature of all the malignant cells, and this phenomenon can be used as a simple and rapid device for the detection of malignancy.
TL;DR: The glyoxalase I gene (gloA) from Salmonella typhimurium has been isolated in Escherichia coli on a multi-copy pBR322-derived plasmid, selecting for resistance to 3 mM methylglyoxal on Luria-Bertani agar.
TL;DR: Quantitative treatment of the data by means of the Stokes-Einstein diffusion law suggests that catalysis will be about 50% diffusion limited under conditions where [substrate] << Km; this is consistent with a model of the glyoxalase pathway in which the enzyme-catalyzed steps are significantly diffusionlimited under physiological conditions.
Abstract: The diffusion-dependent kinetic properties of the yeast glyoxalase I reaction have been measured by means of viscosometric methods. For the glyoxalase-I-catalyzed isomerization of glutathione (GSH)-methylglyoxal thiohemiacetal to S-d-lactoylglutathione, the kcat/Km (3.5 × 106 M−1 S−1, pH7, 25°C) undergoes a progressive decrease in magnitude with increasing solution viscosity, using sucrose as a visco-genic agent. The viscosity effect is unlikely to be due to a sucrose-induced change in the intrinsic kinetic properties of the enzyme, as the magnitude of kcat/Km for the slow substrate GSH-t-butylglyoxal thiohemiacetal (3.5 × 103 M−1 s−1, pH 7, 25°C) is independent of solution viscosity. Quantitative treatment of the data by means of the Stokes-Einstein diffusion law suggests that catalysis will be about 50% diffusion limited under conditions where [substrate] «Km; the encounter complex between enzyme and substrate partitions nearly equally between product formation and dissociation to form free enzyme and substrate. In a related study, the steady-state concentrations of glyoxalase-pathway intermediates in glycolyzing human erythrocytes are estimated to be in the nanomolar concentration range, on the basis of published values for the activities of glyoxalase I and glyoxalase II in lysed erythrocytes and the steady-state rate of formation of d-lactate in intact erythrocytes. This is consistent with a model of the glyoxalase pathway in which the enzyme-catalyzed steps are significantly diffusion limited under physiological conditions.
TL;DR: The effect of methylglyoxal on heart mitochondria as described in the present paper is strikingly similar to the results of previous work with mitochondria of Ehrlich ascites carcinoma cells and leukemic leukocytes, which apparently provides a solid experimental foundation for the proposed hypothesis that excessive ATP formation in cells may lead to malignancy.
Abstract: The effect of methylglyoxal on the oxygen consumption of mitochondria of heart and of several other organs of normal animals of different species has been tested. The results indicate that methylglyoxal (3.5 mM) strongly inhibits ADP-stimulated α-oxoglutarate and malate plus pyruvate-dependent respiration of exclusively heart mitochondria of normal animals of different species. Whereas, with the same substrates, but at a higher concentration of methylglyoxal (7.5 mM), the respiration of mitochondria of other organs of normal animals is not inhibited. Methylglyoxal also inhibits the respiration of slices of rat and toad hearts. But this inhibition is less pronounced. However, methylglyoxal (15 mM) fails to have any effect on perfused toad heart. Using rat heart mitochondria as a model, the effect of methylglyoxal on the oxygen consumption was also tested with different respiratory substrates, electron donors at different segments of the mitochondrial respiratory chain and site-spe inhibitors to identify the specific respiratory complex which might be involved in the inhibitory effect of methylglyoxal. The results strongly suggest that methylglyoxal inhibits the electron flow through complex I of rat heart mitochondrial respiratory chain. Moreover, lactaldehyde (0.6 mM), a catabolite of methylglyoxal, can exert a protective effect on the inhibition of rat heart mitochondrial respiration by methylglyoxal (2.5 mM). The effect of methylglyoxal on heart mitochondria as described in the present paper is strikingly similar to the results of our previous work with mitochondria of Ehrlich ascites carcinoma cells and leukemic leukocytes. We have recently proposed a new hypothesis on cancer which suggests that excessive ATP formation in cells may lead to malignancy. The above mentioned similarity apparently provides a solid experimental foundation for the proposed hypothesis which has been discussed.
TL;DR: The results show that Lys-2 and Lys-163 play almost equal roles in cross-linking of γB-crystallin, and for the first time that significant cross- linking occurs between lysines and non-lysine sites.
Journal Article•
TL;DR: Evidence is found indicating that the incomplete recovery of cell growth by the addition of polyamines to the polyamine-depleted cells was due to programmed cell death (apoptosis) induced by MGBCP.
Abstract: Our previous experiments have shown that methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), a polyamine synthesis inhibitor, suppresses the growth of osteosarcoma cells repressing their intracellular polyamine levels, and that this inhibition of cell growth is only partially reversed by the addition of polyamines. In the present study, we found evidence indicating that the incomplete recovery of cell growth by the addition of polyamines to the polyamine-depleted cells was due to programmed cell death (apoptosis) induced by MGBCP. Morphological changes showing blebbing and chromatin condensation were observed in MGBCP-treated cells, and hypodiploid subpopulations containing apoptotic cells were clearly visible in the profile of flow cytometric analysis. Characteristic oligonucleosomal-sized fragments were increased as the concentration of MGBCP was increased. The results presented here suggest that in addition to reducing the growth rates, MGBCP can induce apoptotic cell death in three human osteosarcoma cell lines.
TL;DR: It is suggested that MGBCP exhibits an anti‐proliferative effect on H. pylori by suppression of macromolecule synthesis.
Abstract: The anti-proliferative effect of methylglyoxal bis(cyclopentylamidino-hydrazone) (MGBCP), a multi-enzyme inhibitor of polyamine biosynthesis, on the growth of Helicobacter pylori was investigated. MGBCP inhibited the cell growth of H. pylori in a dose-dependent manner. The inhibition was partially reversed by the addition of spermidine. Synthesis of macromolecules, DNA, RNA and protein, was inhibited in the spermidine-depleted H. pylori cells. These findings suggest that MGBCP exhibits an anti-proliferative effect on H. pylori by suppression of macromolecule synthesis.
Patent•
25 Apr 1997
TL;DR: In this article, water is introduced in an amount sufficient to form an acidic reaction mixture in which the acetal product and water form an azeotropic mixture, with or without the retention of some methanol reactant.
Abstract: In a process for the preparation of methylglyoxal dimethyl acetal from methylglyoxal and methanol in the presence of an acidic ion exchanger, water is introduced in an amount sufficient to form an acidic reaction mixture in which the acetal product and water form an azeotropic mixture, with or without the retention of some methanol reactant. After subjecting a single phase acidic reaction mixture to an azeotropic distillation, it will separate into two distinct liquid phases with a simple recovery of the acetal product from the aqueous phase.
TL;DR: It was found that D-form is mainly present in Octopus vulgaris and very little L-lactate was found in octopus muscle, and there is an inverse relationship between octopus and normal animals for concentrations of D-and L- lactate.
Abstract: It has long been known that only L-lactic acid is found in animals and that D-lactic acid is produced in microbial organisms. During the course of study of D-lactate formation from methylglyoxal (the methylglyoxal bypass) in animals, we found that D-form is mainly present in Octopus vulgaris and very little L-lactate was found in octopus muscle. There is an inverse relationship between octopus and normal animals for concentrations of D-and L-lactate. The activities of D-lactate dehydrogenase (D-LDH) was predominantly found in octopus muscle, while L-LDH activity was scarcely detected. Methylglyoxal was the best substrate for D-lactate formation in octopus foot homogenate and pyruvate was the second best substrate. It was also found that D-lactate is present in much higher amounts than the L-form in some animals or plants.
TL;DR: To decrease the mutagenic activity and make it possible to use genetically engineered yeasts for practical fermentation processes, a mutant having a decreased level of methylglyoxal synthase activity was isolated.
Abstract: Summary Methylglyoxal synthase catalyses the transformation of dihydroxyacetonephosphate to methylglyoxal, a toxic 2-oxoaldehyde which is found to be present in the yeast Saccharomyces cerevisiae DKD-5D-H. Yeast cells in which genes for phosphoglucose isomerase, phosphofructokinase and triosephosphate isomerase had been extrachromosomally amplified by using a multi-copy plasmid showed an increased ability to induce mutagenesis in standard tests when compared to wild type yeast. This response is mainly due to the increased amount of methylglyoxal in the engineered cells. To decrease the mutagenic activity and make it possible to use genetically engineered yeasts for practical fermentation processes, a mutant having a decreased level of methylglyoxal synthase activity was isolated. When transformed with genes for the glycolytic enzymes, the mutant cells showed extremely low levels of methylglyoxal content and mutagenic activity, both levels being comparable with those of non-transformed DKD-5D-H cells.
TL;DR: In this paper, the reactions of methylglyoxal in aqueous solutions of Tris [tris(hydroxymethyl)aminomethane] buffer were examined at 600 MHz by two-dimensional NMR experiments selected to circumvent the difficulties associated with spectral assignment in the presence of intense resonances due to both solvent and buffer.
Abstract: The reactions of methylglyoxal in aqueous solutions of Tris [tris(hydroxymethyl)aminomethane] buffer were examined at 600 MHz by two-dimensional NMR experiments selected to circumvent the difficulties associated with spectral assignment in the presence of intense resonances due to both solvent and buffer. Methylglyoxal, generatedin situfrom glyceraldehyde 3-phosphate, reacted with Tris to yield principally a mixture of 3,6-dioxa-8-azabicyclo[3.2.1]octanes. 1H and 13C NMR parameters are reported for three compounds containing this little-known ring system and structural influences compared with those in related compounds. A much slower reaction led to the ultimate formation ofN-[tris(hydroxymethyl)methyl]alanine. Implications for various enzyme assays are considered and the results are compared with previous observations of reactions of α-dicarbonyl compounds with α-amino alcohols. © 1997 by John Wiley & Sons, Ltd.