Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
 4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscle branched-chain amino acid metabolism is coupled to alanine formation via branched-chain amino acid aminotransferase and alanine aminotransferase, but the subcellular distributions of these and other associated enzymes are uncertain. Recovery of branched-chain aminotransferase in the cytosol fraction after differential centrifugation was shown to be accompanied by leakage of mitochondrial-matrix marker enzymes. By using a differential fractional extraction procedure, most of the branched-chain aminotransferase activity in rat muscle was located in the mitochondrial compartment, whereas alanine aminotransferase was predominantly in the cytosolic compartment. Phosphoenolpyruvate carboxykinase, like aspartate aminotransferase, was approximately equally distributed between these subcellular compartments. This arrangement necessitates a transfer of branched-chain amino nitrogen and carbon from the mitochondria to the cytosol for alanine synthesis de novo to occur. In incubations of hemidiaphragms from 48 h-starved rats with 3mM-valine or 3mM-glutamate, the stimulation of alanine release was inhibited by 69% by 1 mM-aminomethoxybut-3-enoate, a selective inhibitor of aspartate aminotransferase. Leucine-stimulated alanine release was unaffected. These data implicate aspartate aminotransferase in the transfer of amino acid carbon and nitrogen from the mitochondria to the cytosol, and suggest that oxaloacetate, via phosphoenolpyruvate carboxykinase, can serve as an intermediate on the route of pyruvate formation for muscle alanine synthesis.
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PMID:Branched-chain amino acid metabolism and alanine formation in rat muscles in vitro. Mitochondrial-cytosolic interrelationships. 397 57

A specially designed model reactor based on a 42-L laboratory fermentor was equipped with six stirrers (Rushton turbines) and five cylindrical disks. In this model reactor, the mixing time, Theta(90), turned out to be 13 times longer compared with the 42-L standard laboratory fermentor fitted with two Rushton turbines and four wall-fixed longitudinal baffles. To prove the suitability of the model reactor for scaledown studies of mixing-time-dependent processes, parallel exponential fed-batch cultivations were carried out with the leucine-auxotrophic strain, Corynebacterium glutamicum DSM 5715, serving as a microbial test system. L‐Leucine, the process-limiting substrate, was fed onto the liquid surface of both reactors. Cultivations were conducted using the same inoculum material and equal oxygen supply. The model reactor showed reduced sugar consumption (-14%), reduced ammonium consumption (-19%), and reduced biomass formation (-7%), which resulted in a decrease in L-lysine formation (-12%). These findings were reflected in less specific enzyme activity, which was determined for citrate synthase (CS), phosphoenolpyruvate carboxylase (PEP-C), and aspartate kinase (AK). The reduced specific activity of CS correlated with lower CO(2) evolution (-36%) during cultivation. The model reactor represents a valuable tool to simulate the conditions of poor mixing and inhomogeneous substrate distribution in bioreactors of industrial scale. Copyright 1999 John Wiley & Sons, Inc.
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PMID:A special reactor design for investigations of mixing time effects in a scaled-down industrial L-lysine fed-batch fermentation process 1040 40

Leucine is rapidly metabolized in astroglial primary cultures. Therefore, it is considered as valuable fuel in brain energy metabolism. Only few of the leucine metabolites generated and released by astroglial cells have been identified. Therefore, a more detailed study was performed analyzing by NMR techniques the 13C-labeled metabolites, which were released by astroglial primary cultures during the degradation of [U-(13)C]leucine. Confirming a former radioactive study this analysis revealed 13C-labeled 2-oxoisocaproate and ketone bodies. Additionally, 13C-labeled alanine, citrate, glutamine, lactate and succinate were identified. Their detailed isotopomer analysis proves that 13C-labeled acetyl-CoA enters the tricarboxylic acid cycle, that intermediates with a characteristic 13C-labeling pattern can be withdrawn at several positions of the cycle, and that in the case of lactate and alanine there appears to be a participation of an active phosphoenolpyruvate carboxykinase and/or malic enzyme pathway. Thus, astroglial cells generate and release into the extracellular fluid not only the leucine catabolites 2-oxoisocaproate and ketone bodies, but also several tricarboxylic acid cycle dependent metabolites.
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PMID:Metabolism of [U-(13)C]leucine in cultured astroglial cells. 1566 40

Using rainbow trout hepatocytes stimulated with l-leucine, l-methionine, or l-lysine in the presence or absence of bovine insulin, we investigated the ability of these amino acids to mimic the effects of a pool of amino acids on protein kinase B (Akt)/target of rapamycin (TOR) signaling pathways and expression of 6 genes known to be subjected to insulin and/or amino acid regulation [glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), glucokinase (GK), pyruvate kinase (PK), fatty acid synthase (FAS), and serine dehydratase (SDH)]. Emphasis was placed on leucine, known to be a signaling molecule in mammals, and methionine and lysine that are essential amino acids limiting in plant-based diets for fish. In the presence of insulin, leucine (but not methionine or lysine) phosphorylated Akt and ribosomal protein S6 as previously observed with a pool of amino acids, suggesting that leucine might participate in the activation of the TOR pathway by amino acids in fish, as in mammals. G6Pase, PEPCK, GK, and SDH gene expression were higher in leucine-treated cells compared with control cells. Leucine combined with insulin reduced G6Pase gene expression by 90% and increased FAS gene expression > 4-fold compared with the control treatment. Methionine weakly decreased G6Pase, GK, and SDH gene expression and lysine weakly but significantly decreased the mRNA level of PEPCK. Thus, leucine regulated gluconeogenesis and lipogenesis, but not glycolysis, in the same way as a pool of amino acids. Methionine appeared to be involved in the regulation of specific genes, whereas lysine only had limited effects. These findings are particularly relevant regarding the involvement of amino acids in the regulation of metabolism-related gene expression.
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PMID:L-leucine, L-methionine, and L-lysine are involved in the regulation of intermediary metabolism-related gene expression in rainbow trout hepatocytes. 2110 25