Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.4.1.1 (pyruvate carboxylase)
 1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A protein phosphokinase (EC 2.7.1.1.37) was isolated from baker's yeast (Saccharomyces cerevisiae) after a 17,000-fold purification; the purified enzyme is homogeneous according to the criteria of gel electrophoresis and ultracentrifuge analysis. The enzyme has a high isoelectric point of ca. 9 and appears to exist as a monomer with a molecular weight of 42,000 plus or minus 1500. It is neither stimulated by cyclic 3',5'-AMP, -GMP, -CMP or -ump nor inhibited by the regulatory subunit of rabbit muscle protein kinase (Reimann, E. M., Walsh, D. A., and Krebs, E. G. (1971), J. Biol. Chem. 246, 1986). In the presence of divalent metal ions, preferably Mg-2+ or Mn-2+, the enzyme readily transfers the terminal phosphate group of ATP to phosvitin, alphaS1B- and beta a-casein and an NH2-terminal tryptic peptide derived from beta a-casein, but not to protamine, lysine, or arginine-rich histones or to yeast enzymes such as phosphorylase, phosphofructokinase, or pyruvate carboxylase; serine and polyserine were also inactive as phosphate acceptors. Km values of 0.17 mM for beta a-casein and 0.2 mMfor ATP were determined at 10 mM Mg-2+. The urified yeast protein kinase also catalyzes the reverse reaction, namely, the transfer of phosphate from fully phosphorylated beta a-casein or its NH2-terminal peptide to ADP resulting in the formation of ATP. AMP, GDP, UDP, and CDP did not serve as phosphate acceptors in this reaction. As observed by Rabinowitz and Lipmann (Rabinowitz, M., and Lipmann, F. (1960), J. Biol. Chem. 235, 1043) both reactions have different pHoptima with values of 7.5 for the forward reaction (phosphorylation of the proteins) and ca 5.2 for the formation of ATP; both are differently affected by salts. Phosphorylation of beta a-casein with [gamma-32-P]ATP followed by digestion of the labeled protein with trypsin indicated that all the radioactivity was exclusively introduced in an NH2-terminal peptide possessing the unique sequence: Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu...(Ribadeau-Dumas, B., Brignon, G., Grosclaude, F., and Mercier, J.-C. (1971), eur J. Biochem. 20, 264). By subjecting beta a-casein and its NH2-terminal peptide to the combined action of almond acid phosphatease and purified yeast protein kinase, it was determined that the phosphorylation and dephosphorylation reactions proceed randomly, i.e., all seryl phosphate residues are equally susceptible and that the rate of phosphorylation decreases drastically as the number of bound phosphate groups in the substrate diminishes.
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PMID:Purification and properties of a yeast protein kinase. 23 75

Phosphoenolpyruvate (P-pyruvate) carboxylase from ripened banana fruit was purified to near homogeneity and a final specific activity of 20-23 U/mg protein; P-pyruvate carboxylase-kinase copurified with P-pyruvate carboxylase throughout the purification. Gel filtration FPLC indicated that the two proteins form a tightly associated 425-kDa complex. Both the 103-kDa and 100-kDa subunits of the P-pyruvate carboxylase alpha2beta2 hetetrotetramer were phosphorylated and subsequently dephosphorylated in vitro in a time-dependent manner when the final preparation was incubated with 0.1 mM [gamma-32P]ATP followed by rabbit muscle protein phosphatase type 2A1. Phosphoamino acid and phosphopeptide map analyses indicated that in vitro phosphorylation of both subunits likely occurs at an identical Ser residue. Maximal stoichiometry of 32P incorporation was 0.2 and 0.4 mol/mol 103-kDa and 100-kDa subunit, respectively. The level of 32P incorporation was correlated with the enzyme's activation state when assayed under suboptimal assay conditions (pH 7.3, 75 microM P-pyruvate, 0.2 mM L-malate). The main kinetic effect of phosphorylation was to decrease the enzyme's Km(P-pyruvate), as well as its sensitivity to inhibition by L-malate and L-glutamate. Banana P-pyruvate carboxylase-kinase: (a) also phosphorylated maize leaf P-pyruvate carboxylase, histone III-S, and dephosphorylated casein; (b) demonstrated Mg2+ dependence and Ca2+ independence, (c) exhibited a broad pH activity optimum of pH 8.0-8.5, and (d) was inhibited by L-malate and activated by Ba2+ and Co2+. Time-course kinetic studies suggested that P-pyruvate carboxylase exists mainly in the dephosphorylated form in preclimacteric, climacteric and postclimacteric fruit, but that its kinase is expressed throughout ripening. In situ 32P-labeling indicated that, while both subunits of ripe banana P-pyruvate carboxylase are phosphorylated in vivo, it is primarily the 100-kDa subunit that is radiolabeled. The results suggest that similar to the enzyme from leaves, root nodules and seeds, a fruit P-pyruvate carboxylase may be subject to regulatory seryl phosphorylation by an endogenous P-pyruvate carboxylase-kinase.
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PMID:Regulatory phosphorylation of banana fruit phosphoenolpyruvate carboxylase by a copurifying phosphoenolpyruvate carboxylase-kinase. 926 8

Bears undergo annual cycles in body mass: rapid fattening in autumn (i.e., hyperphagia), and mass loss in winter (i.e., hibernation). To investigate how Japanese black bears (Ursus thibetanus japonicus) adapt to such extreme physiological conditions, we analyzed changes in the mRNA expression of energy metabolism-related genes in white adipose tissues and skeletal muscle throughout three physiological stages: normal activity (June), hyperphagia (November), and hibernation (March). During hyperphagia, quantitative real-time polymerase chain reaction analysis revealed the upregulation of de novo lipogenesis-related genes (e.g., fatty acid synthase and diacylglycerol O-acyltransferase 2) in white adipose tissue, although the bears had been maintained with a constant amount of food. In contrast, during the hibernation period, we observed a downregulation of genes involved in glycolysis (e.g., glucose transporter 4) and lipogenesis (e.g., acetyl-CoA carboxylase 1) and an upregulation of genes in fatty acid catabolism (e.g., carnitine palmitoyltransferase 1A) in both tissue types. In white adipose tissues, we observed upregulation of genes involved in glyceroneogenesis, including pyruvate carboxylase and phosphoenolpyruvate carboxykinase 1, suggesting that white adipose tissue plays a role in the recycling of circulating free fatty acids via re-esterification. In addition, the downregulation of genes involved in amino acid catabolism (e.g., alanine aminotransferase) and the TCA cycle (e.g., pyruvate carboxylase) indicated a role of skeletal muscle in muscle protein sparing and pyruvate recycling via the Cori cycle. These examples of coordinated transcriptional regulation would contribute to rapid mass gain during the pre-hibernation period and to energy preservation and efficient energy production during the hibernation period.
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PMID:Seasonal changes in the expression of energy metabolism-related genes in white adipose tissue and skeletal muscle in female Japanese black bears. 2688 Mar 64