Showing papers on "Malic enzyme published in 2020"
TL;DR: It is established that osteoblast differentiation under aerobic conditions is coupled with a marked increase in glucose consumption and lactate production but reduced oxygen consumption, and the mitochondrial malic enzyme functionally couples the mitochondria with aerobic glycolysis in osteoblasts.
73 citations
TL;DR: Xizhoumi et al. as mentioned in this paper investigated the molecular information of soluble sugars and organic acids both in stored fresh-cut and whole melon fruits, the enzymes and genes involved in the metabolism of sucrose and organic acid in melon fruit were investigated.
30 citations
TL;DR: The results indicated that Put catabolism along with improved N assimilation and the accumulation of GABA and MA were the key metabolic processes in roots of AM maize plants in response to water stress.
Abstract: Water shortage limits plant growth and development by inducing physiological and metabolic disorders, while arbuscular mycorrhizal (AM) symbiosis can improve plant adaptation to drought stress by altering some metabolic and signaling pathways. In this study, root growth and levels of some metabolites (polyamines, amino acids, and malic acid [MA]) and key enzymes were examined in AM-inoculated and non-inoculated (NM) maize seedlings under different water conditions. The results showed that AM symbiosis stimulated root growth and the accumulation of putrescine (Put) during initial plant growth. Root Put concentration significantly decreased in AM compared with NM plants under water stress; correspondingly, Put degradation via diamine oxidase into γ-aminobutyric acid (GABA) occurred. Moreover, glutamine concentration and the activity of N assimilation enzymes (nitrate reductase and glutamine synthetase) were higher in roots of AM than NM plants under moderate water stress. The activity of GABA transaminase and malic enzyme, and MA concentration were also higher in roots of AM than NM plants under moderate water stress. Our results indicated that Put catabolism along with improved N assimilation and the accumulation of GABA and MA were the key metabolic processes in roots of AM maize plants in response to water stress.
29 citations
TL;DR: Dynamic metabolome analyses revealed that overexpression of ME led to increased turnover rates in malate and pyruvate metabolism; in contrast, deletion of ME resulted in increased pool sizes of glycolytic intermediates, probably due to sequential feedback inhibition, initially triggered by malate accumulation.
Abstract: d-Lactate is one of the most valuable compounds for manufacturing biobased polymers. Here, we have investigated the significance of endogenous malate dehydrogenase (decarboxylating) (malic enzyme, ME), which catalyzes the oxidative decarboxylation of malate to pyruvate, in d-lactate biosynthesis in the cyanobacterium Synechocystis sp. PCC6803. d-Lactate levels were increased by 2-fold in ME-overexpressing strains, while levels in ME-deficient strains were almost equivalent to those in the host strain. Dynamic metabolomics revealed that overexpression of ME led to increased turnover rates in malate and pyruvate metabolism; in contrast, deletion of ME resulted in increased pool sizes of glycolytic intermediates, probably due to sequential feedback inhibition, initially triggered by malate accumulation. Finally, both the loss of the acetate kinase gene and overexpression of endogenous d-lactate dehydrogenase, concurrent with ME overexpression, resulted in the highest production of d-lactate (26.6 g/L) with an initial cell concentration of 75 g-DCW/L after 72 h fermentation.
22 citations
TL;DR: Recent findings are integrated to highlight ME1's role in oncogenesis, provide a rationale for its nexus with metabolic syndrome and diabetes, and raise the prospects of targeting the cytosolic NADPH network to improve therapeutic approaches against multiple cancers.
Abstract: Malic enzyme 1 (ME1) is a cytosolic protein that catalyzes the conversion of malate to pyruvate while concomitantly generating NADPH from NADP. Early studies identified ME1 as a mediator of intermediary metabolism primarily through its participatory roles in lipid and cholesterol biosynthesis. ME1 was one of the first identified insulin-regulated genes in liver and adipose and is a transcriptional target of thyroxine. Multiple studies have since documented that ME1 is pro-oncogenic in numerous epithelial cancers. In tumor cells, the reduction of ME1 gene expression or the inhibition of its activity resulted in decreases in proliferation, epithelial-to-mesenchymal transition and in vitro migration, and conversely, in promotion of oxidative stress, apoptosis and/or cellular senescence. Here, we integrate recent findings to highlight ME1's role in oncogenesis, provide a rationale for its nexus with metabolic syndrome and diabetes, and raise the prospects of targeting the cytosolic NADPH network to improve therapeutic approaches against multiple cancers.
20 citations
TL;DR: The results indicate that NADP-ME1 is involved in adjusting the malate levels in the root apex, and its loss results in an increased content of this organic acid, and suggest that NADp-me1 affects signaling processes, such as the generation of reactive oxygen species and those that involve glutamate, which could lead to root growth inhibition.
Abstract: In acidic soils, aluminum (Al) toxicity is a significant limitation to crop production worldwide. Given its Al-binding capacity, malate allows internal as well as external detoxification strategies to cope with Al stress, but little is known about the metabolic processes involved in this response. Here, we analyzed the relevance of NADP-dependent malic enzyme (NADP-ME), which catalyzes the oxidative decarboxylation of malate, in Al tolerance. Plants lacking NADP-ME1 (nadp-me1) display reduced inhibition of root elongation along Al treatment compared with the wild type (wt). Moreover, wt roots exposed to Al show a drastic decrease in NADP-ME1 transcript levels. Although malate levels in seedlings and root exudates are similar in nadp-me1 and wt, a significant increase in intracellular malate is observed in roots of nadp-me1 after long exposure to Al. The nadp-me1 plants also show a lower H2 O2 content in root apices treated with Al and no inhibition of root elongation when exposed to glutamate, an amino acid implicated in Al signaling. Proteomic studies showed several differentially expressed proteins involved in signal transduction, primary metabolism and protection against biotic and other abiotic stimuli and redox processes in nadp-me1, which may participate directly or indirectly in Al tolerance. The results indicate that NADP-ME1 is involved in adjusting the malate levels in the root apex, and its loss results in an increased content of this organic acid. Furthermore, the results suggest that NADP-ME1 affects signaling processes, such as the generation of reactive oxygen species and those that involve glutamate, which could lead to inhibition of root growth.
7 citations
TL;DR: It is shown that blockadge of Me1 led to the accumulation of mitochondrial O2- level and decreased ATP production and mtDNA copy numbers accompanied with defective mitochondrial membrane potential, and Me1 played a role in maintaining mitochondrial function.
Abstract: Malic enzyme 1 (Me1), a member of the malic enzymes involving in glycolytic pathway and citric acid cycle, is essential for the energy metabolism and maintenance of intracellular redox balance state, but its physiological role and regulatory mechanism in the uterine decidualization are still unknown. Current study showed that Me1 was strongly expressed in decidual cells, and could promote the proliferation and differentiation of stromal cells followed by an accelerated cell cycle transition, indicating an importance of Me1 in the uterine decidualization. Silencing of Me1 attenuated NADPH generation and reduced GR activity, while addition of NADPH improved the defect of GR activity elicited by Me1 depletion. Further analysis found that Me1 modulated intracellular GSH content via GR. Meanwhile, Me1 played a role in maintaining mitochondrial function as indicated by these observations that blockadge of Me1 led to the accumulation of mitochondrial O 2 - level and decreased ATP production and mtDNA copy numbers accompanied with defective mitochondrial membrane potential. In uterine stromal cells, progesterone induced Me1 expression through PR-cAMP-PKA pathway. Knockdown of HB-EGF might impede the regulation of progesterone and cAMP on Me1. Collectively, Me1 is essential for uterine decidualization in response to progesterone/cAMP/PKA/HB-EGF pathway and plays an important role in preventing mitochondrial dysfunction.
7 citations
TL;DR: This study is the first to establish the regulatory effects of sRNAs on mRNAs during the oxidative stress response in Archaea and indicates that SHOxi likely regulates redox homeostasis during oxidative stress by the post-transcriptional destabilization of malic enzyme mRNA.
Abstract: Haloarchaea are highly resistant to oxidative stress, however, a comprehensive understanding of the processes regulating this remarkable response is lacking. Oxidative stress-responsive small non-coding RNAs (sRNAs) have been reported in the model archaeon, Haloferax volcanii, but targets and mechanisms have not been elucidated. Using a combination of high throughput and reverse molecular genetic approaches, we elucidated the functional role of the most up-regulated intergenic sRNA during oxidative stress in H. volcanii, named Small RNA in Haloferax Oxidative Stress (SHOxi). SHOxi was predicted to form a stable secondary structure with a conserved stem-loop region as the potential binding site for trans-targets. NAD-dependent malic enzyme mRNA, identified as a putative target of SHOxi, interacted directly with a putative “seed” region within the predicted stem loop of SHOxi. Malic enzyme is an enzyme of the tricarboxylic acid cycle that catalyzes the oxidative decarboxylation of malate into pyruvate using NAD+ as a cofactor. The destabilization of malic enzyme mRNA, and the decrease in the NAD+/NADH ratio, resulting from the direct RNA-RNA interaction between SHOxi and its trans-target was essential for the survival of H. volcanii to oxidative stress. These findings indicate that SHOxi likely regulates redox homeostasis during oxidative stress by the post-transcriptional destabilization of malic enzyme mRNA. SHOxi-mediated regulation provides evidence that the fine-tuning of metabolic cofactors could be a core strategy to mitigate damage from oxidative stress and confer resistance. This study is the first to establish the regulatory effects of sRNAs on mRNAs during the oxidative stress response in Archaea.
6 citations
TL;DR: Phylogenetic analyses of haloarchaeal malic enzymes indicate a separate evolutionary line distinct from other archaeal homologs, and the exclusive function of phosphoenolpyruvate synthetase in gluconeogenesis was proven by the respective knock-out mutant.
Abstract: The haloarchaeon Haloferax volcanii grows on acetate as sole carbon and energy source. The genes and proteins involved in uptake and activation of acetate and in gluconeogenesis were identified and analyzed by characterization of enzymes and by growth experiments with the respective deletion mutants. (i) An acetate transporter of the sodium: solute-symporter family (SSF) was characterized by kinetic analyses of acetate uptake into H. volcanii cells. The functional involvement of the transporter was proven with a Δssf mutant. (ii) Four paralogous AMP-forming acetyl-CoA synthetases that belong to different phylogenetic clades were shown to be functionally involved in acetate activation. (iii) The essential involvement of the glyoxylate cycle as an anaplerotic sequence was concluded from growth experiments with an isocitrate lyase knock-out mutant excluding the operation of the methylaspartate cycle reported for Haloarcula species. (iv) Enzymes involved in phosphoenolpyruvate synthesis from acetate, namely two malic enzymes and a phosphoenolpyruvate synthetase, were identified and characterized. Phylogenetic analyses of haloarchaeal malic enzymes indicate a separate evolutionary line distinct from other archaeal homologs. The exclusive function of phosphoenolpyruvate synthetase in gluconeogenesis was proven by the respective knock-out mutant. Together, this is a comprehensive study of acetate metabolism in archaea.
6 citations
TL;DR: It was found for the first time that the addition of trivalent aluminium and iron ions accelerates ME-catalyzed carboxylation of pyruvate with CO2 and will lead to new insight into biocatalytic CO2 utilization research.
Abstract: Malic enzyme (ME) from chicken liver (EC 1.1.1.40) is an enzyme that catalyzes the decarboxylation of malate into pyruvate and CO2 and the reverse reaction that introduces CO2 as a carboxy-group to pyruvate to form malate via oxaloacetate in the presence of natural co-enzyme NADP+/NADPH. Thus, ME is an attractive biocatalyst for building carbon–carbon bonds through the carboxylation of pyruvate with CO2. Since ME mainly catalyzes the decarboxylation of malate to produce pyruvate via oxaloacetate, it is necessary to devise ways to promote the carboxylation of pyruvate with CO2 to produce oxaloacetate based on the building of carbon–carbon bonds. Enhancing the carboxylation of pyruvate by the addition of metal ions with CO2 and using ME as a catalyst will lead to new insight into biocatalytic CO2 utilization research. The effect of adding divalent and trivalent metal ions to promote the ME-catalyzed building of carbon–carbon bonds through the carboxylation of pyruvate with CO2 was investigated. Specifically, it was found for the first time that the addition of trivalent aluminium and iron ions accelerates ME-catalyzed carboxylation of pyruvate with CO2. Moreover, it was found that a high concentration of aluminum ions (>100 μM) and a low concentration of iron ions (<10 μM) promote the ME-catalyzed carboxylation of pyruvate with CO2.
5 citations
TL;DR: Results suggest that PEP carboxylase (SCO3127) is an important enzyme during glucose catabolism and oxaloacetate replenishment and NADP+-malic enzyme could have an important role in gluconeogenesis in S. coelicolor.
Abstract: The phosphoenolpyruvate-pyruvate-oxaloacetate node is a major branch within the central carbon metabolism and acts as a connection point between glycolysis, gluconeogenesis, and the TCA cycle. Phosphoenolpyruvate carboxylase, pyruvate carboxylase, phosphoenolpyruvate carboxykinase, malic enzymes, and pyruvate kinase, among others, are enzymes included in this node. We determined the mRNA levels and specific activity profiles of some of these genes and enzymes in Streptomyces coelicolor M-145. The results obtained in the presence of glucose demonstrated that all genes studied of the phosphoenolpyruvate-pyruvate-oxaloacetate node were expressed, although at different levels, with 10- to 100-fold differences. SCO3127 (phosphoenolpyruvate carboxylase gene) and SCO5261 (NADP+-dependent malic enzyme gene) showed the highest expression in the rapid growth phase, and the mRNA levels corresponding to SCO5896 (phosphoenolpyruvate-utilizing enzyme gene), and SCO0546 (pyruvate carboxylase gene) increased 5- to 10-fold towards the stationary phase. In casamino acids, in general mRNA levels of S. coelicolor were lower than in glucose, however, results showed greater mRNA expression of SCO4979 (PEP carboxykinase), SCO0208 (pyruvate phosphate dikinase gene), and SCO5261 (NADP+-dependent malic enzyme). These results suggest that PEP carboxylase (SCO3127) is an important enzyme during glucose catabolism and oxaloacetate replenishment. On the other hand, phosphoenolpyruvate carboxykinase, pyruvate phosphate dikinase, and NADP+-malic enzyme could have an important role in gluconeogenesis in S. coelicolor.
TL;DR: The data support that the phosphotransacetylase domain of MaeB-like enzymes senses acetyl-CoA to dictate the fate of carbon distribution at the phosphoenol-pyruvates / pyruvate / oxaloacetate metabolic node.
TL;DR: Results indicate that LmCA1 by virtue of its CO2 concentrating ability stimulates LmME-catalyzed pyruvate carboxylation, thereby driving gluconeogenesis through pyruVate-malate-oxaloacetate bypass pathway.
Abstract: Leishmania has a remarkable ability to proliferate under widely fluctuating levels of essential nutrients, such as glucose For this the parasite is heavily dependent on its gluconeogenic machinery One perplexing aspect of gluconeogenesis in Leishmania is the lack of the crucial pyruvate carboxylase (PC) gene PC-catalyzed conversion of pyruvate to oxaloacetate is a key entry point through which gluconeogenic amino acids are funnelled into this pathway Absence of PC in Leishmania thus raises question about the mechanism of pyruvate entry into the gluconeogenic route We report here that this task is accomplished in Leishmania major through a novel functional partnership between its mitochondrial malic enzyme (LmME) and cytosolic carbonic anhydrase (LmCA1) Using a combination of pharmacological inhibition studies with genetic manipulation, we showed that both these enzymes are necessary in promoting gluconeogenesis and supporting parasite growth under glucose limiting condition Functional crosstalk between LmME and LmCA1 was evident when it was observed that the growth retardation caused by inhibition of any one of these enzymes could be protected to a significant extent by overexpressing the other enzyme We also found that while LmCA1 exhibited constitutive expression, LmME protein level was strongly upregulated in low glucose condition Notably, both LmME and LmCA1 were found to be important for survival of Leishmania amastigotes within host macrophages Taken together, our results indicate that LmCA1 by virtue of its CO2 concentrating ability stimulates LmME-catalyzed pyruvate carboxylation, thereby driving gluconeogenesis through pyruvate-malate-oxaloacetate bypass pathway Additionally, our study establishes LmCA1 and LmME as promising therapeutic targets
TL;DR: The significance of the pentose phosphate pathway and related NADPH‐regenerating enzymes in the liver under oxidative stress is determined and isocitrate dehydrogenase 1 was most sensitive to glutathione depletion caused by acetaminophen, but glucose 6‐phosphate dehydrogenases, the regulatory enzyme of PPP, was not.
Abstract: The liver regenerates NADPH via multiple pathways to maintain redox balance and reductive biosynthesis. The pentose phosphate pathway (PPP) contributes to hepatic lipogenesis by supplying NADPH, and it is thought to play a major role in response to oxidative stress. This study determined the significance of the PPP and related NADPH-regenerating enzymes in the liver under oxidative stress. Fasted hamsters received acetaminophen (400 mg/kg) to deplete glutathione in the liver and [U-13 C3 ]glycerol to measure the PPP activity by analysis of 13 C distribution in plasma glucose. Blood and liver were harvested to assess NADPH-producing enzymes, antioxidant defense, PPP, and other relevant biochemical processes. Acetaminophen caused glutathione depletion and decreased activities of glutathione peroxidase and catalase in the liver, but it did not change triglyceride synthesis. Although the PPP is potentially an abundant source of NADPH, its activity was decreased and the expression of glucose 6-phosphate dehydrogenase remained unchanged after acetaminophen treatment. The effects of acetaminophen on other NADPH-producing enzymes were complex. Isocitrate dehydrogenase 1 was overexpressed, both isocitrate dehydrogenase 2 and malic enzyme 1 were underexpressed, and methylenetetrahydrofolate dehydrogenase 1 remained unchanged. In summary, isocitrate dehydrogenase 1 was most sensitive to glutathione depletion caused by acetaminophen, but glucose 6-phosphate dehydrogenase, the regulatory enzyme of PPP, was not.
01 Sep 2020
TL;DR: The result indicates that the intrusion of the phytoconstituents in the function of enzymes of energy generating pathway of R. echinobothrida, perhaps dispossesses the parasite from energy production leading to paralysis.
Abstract: The current investigation aims to evaluate the effect of leaf extract of the anthelmintic medicinal plant Lysimachia ramosa and its n-butanol fraction on glycogen concentration and carbohydrate related metabolic enzymes viz. hexokinase (HK), phosphofructokinase, pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (PEPCK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), malic enzyme (ME) and fumarate reductase (FR) in the cestode Raillietina echinobothrida. Following exposure to crude leaf extract and n-butanol fraction at a dose of 6 mg/ml of phosphate buffered saline, glycogen concentration decreased by 26–51% post paralysis whereas in terms of carbohydrate related metabolic enzymes, highest inhibition was seen in case of MDH (66–75%) followed by FR (64–66%), PEPCK (54–64%), LDH (48–60%), ME (33–38%) and PK (27–36%). The decrease in the enzyme activities of HK, LDH and MDH were also demonstrated histochemically. The result indicates that the intrusion of the phytoconstituents in the function of enzymes of energy generating pathway of R. echinobothrida, perhaps dispossesses the parasite from energy production leading to paralysis.
TL;DR: In this paper, the effects of diets containing various carbohydrate-to-lipid (CHO L-1) ratios on growth performance, nutrient utilization body indices and hepatic lipogenic enzyme (malic enzyme, 6-phosphogluconate dehydrogenase and fatty acid synthase) activities were evaluated.
Abstract: This study evaluated the effects of diets containing various carbohydrate-to-lipid (CHO L-1) ratios on growth performance, nutrient utilization body indices and hepatic lipogenic enzyme (malic enzyme, 6-phosphogluconate dehydrogenase and fatty acid synthase) activities. Triplicate groups of Pangasianodon hypophthalmus fingerlings were fed eight isoenergetic and isonitrogenous diets with different carbohydrate-to-lipid ratios (0.51, 0.79, 1.12, 1.79, 2.41, 3.24, 4.43 and 7.62). Higher body fat deposition and lower growth performance were observed in P. hypophthalmus fingerlings fed with high-lipid diet than those fed with high-carbohydrate diet. The fish fed the diet with 7.62 CHO L-1 ratio exhibited significantly (p<0.05) higher hepatosomatic index compared to those fed higher lipid diets (0.51 and 0.79). High dietary carbohydrate level significantly increased (p<0.05) the activities of malic, 6-phosphogluconate dehydrogenase and fatty acid synthase enzyme. Based on the second-order polynomial regression analysis of weight gain, the optimal dietary carbohydrate and lipid contents for P. hypophthalmus fingerling were 304 and 103 g kg−1, respectively, which correspond to a dietary CHO L-1 ratio of 2.95.
Patent•
10 Apr 2020
TL;DR: Improved yeast cell with increased succinic acid production based on yield and titer is discussed in this paper, where the authors show that increased activity of one or more enzymes involved in the pentose phosphate pathway, reducing flux through phosphoglucose isomerase, increasing flux to cytoplasmic acetyl-CoA, installation of a malic enzyme, and/or installation of formate dehydrogenase leads to increased production of succinic acids.
Abstract: Improved yeast cell with increased succinic acid production based on yield and titer. Increased activity of one or more enzymes involved in the pentose phosphate pathway, reducing flux through phosphoglucose isomerase, increasing flux to cytoplasmic acetyl-CoA, installation of a malic enzyme, and/or installation of a formate dehydrogenase leads to increased production of succinic acid.