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A reappraisal of the reaction pathway of pyruvate carboxylase.

ABSTRACT: The reaction pathway catalysed by pyruvate carboxylase was re-examined by using two independent experimental approaches not previously applied to this enzyme. To avoid the variable stoicheiometry associated with oxaloacetate formation, the reaction rate was measured by following release of Pi. Initial velocities, when plotted as a function of varying concentrations of either MgATP2- or HCO3-, at fixed concentrations of pyruvate, gave in double-reciprocal-form families of straight intersecting lines. Further, when the reaction velocity was determined as a function of varying MgATP2- concentrations by using pyruvate, 3-fluoropyruvate and 2-oxobutyrate as alternative carboxyl-acceptor substrates, the slopes of the double-reciprocal plots were significantly different. Both results support a sequential reaction pathway.

SUBMITTER: Easterbrook-Smith SB

PROVIDER: S-EPMC1184212 | biostudies-other | 1978 Jan

REPOSITORIES: biostudies-other

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Pig liver pyruvate carboxylase. The reaction pathway for the carboxylation of pyruvate.

Project description:1. The reaction pathway for the carboxylation of pyruvate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgATP(2-) binds next, followed by HCO(3) (-) and then pyruvate. Oxaloacetate is released before the random release, at equilibrium, of P(i) and MgADP(-). 3. This reaction pathway is compared with the double displacement (Ping Pong) mechanisms that have previously been described for pyruvate carboxylases from other sources. The reaction pathway proposed for the pig liver enzyme is superior in that it shows no kinetic inconsistencies and satisfactorily explains the low rate of the ATP[unk][(32)P]P(i) equilibrium exchange reaction. 4. Values are presented for the stability constants of the magnesium complexes of ATP, ADP, acetyl-CoA, P(i), pyruvate and oxaloacetate.

| S-EPMC1166286 | biostudies-other

Pig liver pyruvate carboxylase. The reaction pathway for the decarboxylation of oxaloacetate.

Project description:1. The reaction pathway for the decarboxylation of oxaloacetate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgADP(-) and P(i) bind randomly, at equilibrium, followed by the binding of oxaloacetate. Pyruvate is released before the ordered steay-state release of HCO(3) (-) and MgATP(2-). 3. These results are entirely consistent with studies on the carboxylation of pyruvate presented in the preceding paper (Warren & Tipton, 1974b) and together they allow a quantitative description of the reaction mechanism of pig liver pyruvate carboxylase. 4. In the absence of other substrates of the back reaction pig liver pyruvate carboxylase will decarboxylate oxaloacetate in a manner that is not inhibited by avidin. 5. Reciprocal plots involving oxaloacetate are non-linear curves, which suggest a negatively co-operative interaction between this substrate and the enzyme.

| S-EPMC1166287 | biostudies-other

suppression of Pyruvate carboxylase

Project description:This SuperSeries is composed of the SubSeries listed below.

2023-12-29 | GSE199831 | GEO

The role of biotin and oxamate in the carboxyltransferase reaction of pyruvate carboxylase.

Project description:Pyruvate carboxylase (PC) is a biotin-dependent enzyme that catalyzes the MgATP-dependent carboxylation of pyruvate to oxaloacetate, an important anaplerotic reaction in central metabolism. During catalysis, carboxybiotin is translocated to the carboxyltransferase domain where the carboxyl group is transferred to the acceptor substrate, pyruvate. Many studies on the carboxyltransferase domain of PC have demonstrated an enhanced oxaloacetate decarboxylation activity in the presence of oxamate and it has been shown that oxamate accepts a carboxyl group from carboxybiotin during oxaloacetate decarboxylation. The X-ray crystal structure of the carboxyltransferase domain from Rhizobium etli PC reveals that oxamate is positioned in the active site in an identical manner to the substrate, pyruvate, and kinetic data are consistent with the oxamate-stimulated decarboxylation of oxaloacetate proceeding through a simple ping-pong bi bi mechanism in the absence of the biotin carboxylase domain. Additionally, analysis of truncated PC enzymes indicates that the BCCP domain devoid of biotin does not contribute directly to the enzymatic reaction and conclusively demonstrates a biotin-independent oxaloacetate decarboxylation activity in PC. These findings advance the description of catalysis in PC and can be extended to the study of related biotin-dependent enzymes.

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My favorite pyruvate carboxylase.

Project description: Not available

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suppression of Pyruvate carboxylase

Project description:suppression of Pyruvate carboxylase

| PRJNA821599 | ENA

Insights into the carboxyltransferase reaction of pyruvate carboxylase from the structures of bound product and intermediate analogs.

Project description:Pyruvate carboxylase (PC) is a biotin-dependent enzyme that catalyzes the MgATP- and bicarbonate-dependent carboxylation of pyruvate to oxaloacetate, an important anaplerotic reaction in central metabolism. The carboxyltransferase (CT) domain of PC catalyzes the transfer of a carboxyl group from carboxybiotin to the accepting substrate, pyruvate. It has been hypothesized that the reactive enolpyruvate intermediate is stabilized through a bidentate interaction with the metal ion in the CT domain active site. Whereas bidentate ligands are commonly observed in enzymes catalyzing reactions proceeding through an enolpyruvate intermediate, no bidentate interaction has yet been observed in the CT domain of PC. Here, we report three X-ray crystal structures of the Rhizobium etli PC CT domain with the bound inhibitors oxalate, 3-hydroxypyruvate, and 3-bromopyruvate. Oxalate, a stereoelectronic mimic of the enolpyruvate intermediate, does not interact directly with the metal ion. Instead, oxalate is buried in a pocket formed by several positively charged amino acid residues and the metal ion. Furthermore, both 3-hydroxypyruvate and 3-bromopyruvate, analogs of the reaction product oxaloacetate, bind in an identical manner to oxalate suggesting that the substrate maintains its orientation in the active site throughout catalysis. Together, these structures indicate that the substrates, products and intermediates in the PC-catalyzed reaction are not oriented in the active site as previously assumed. The absence of a bidentate interaction with the active site metal appears to be a unique mechanistic feature among the small group of biotin-dependent enzymes that act on α-keto acid substrates.

| S-EPMC3894693 | biostudies-literature

Pyruvate carboxylase and carbon metabolism in Listeria monocytogenes

Project description:Transcriptional profile of wild type L. monocytogenes (EGDe) and a pycA mutant strain was compared on growth in BHI. The human pathogen L. monocytogenes is a facultatively intracellular bacterium that survives and replicates in the cytosol of many mammalian cells. The listerial metabolism, especially under intracellular conditions , is still poorly understood. Recent studies analyzed the carbon metabolism of L. monocytogenes by the 13C-isotopologue perturbation method in a defined minimal medium containing [U-13C6]glucose. It was shown that these bacteria produce oxaloacetate mainly by carboxylation of pyruvate due to an incomplete tricarboxylic acid cycle. Here we report that a pycA insertion mutant defective in pyruvate carboxylase (PYC) still grows, albeit at a reduced rate, in BHI medium, but is unable to multiply in a defined minimal medium with glucose or glycerol 36 as carbon source. Transcriptional profiling was performed on the pycA mutant and the wild type strain grown in BHI to get a closer insight into the effect of the pycA mutation in Listeria monocytogenes. RNA from the two strains were isolated after growth in BHI and and compared using whole genome oligonucleotide microarrays

2010-02-09 | E-GEOD-19014 | biostudies-arrayexpress

Pyruvate carboxylase and carbon metabolism in Listeria monocytogenes

2010-02-10 | GSE19014 | GEO

suppression of Pyruvate carboxylase in M-wnt tumors

Project description:Metabolic reprogramming an immune evasion are established hallmarks of the tumor microenvironment (TME). Growing evidence supports tumor metabolic dysregulation as an important mediator of tumor immune evasion. High TME levels of lactate potently suppress antitumor immunity. Pyruvate carboxylase (PC), responsible for the anaplerotic conversion of pyruvate to oxaloacetate, is essential for lung metastasis in breast cancer. Conversely, PC may be dispensable in some cells in the TME, with loss of PC associated with immunosuppression. Here we test whether PC suppression alters tumor metabolism and immunosuppression. Using multiple animal models of breast cancer, we identify a dimorphic role for PC expression in mammary cancer cells. PC supports metastatic colonization of the lungs; however, depletion of PC promotes primary tumor growth and suppresses histological and transcriptomic markers of antitumor immunity. We demonstrate that PC is potently suppressed by hypoxia, and that PC suppression is common in solid tumors, particularly those with higher levels of hypoxia. Using metabolomics, high resolution respirometry, and extracellular flux analysis, we show that PC-depleted cells produce more lactate and undergo less oxidative phosphorylation than scramble controls. Finally, we identify lactate metabolism as a targetable dependency of PC-depleted cells, which is sufficient to restore T cell populations to the TME of PC-depleted tumors. Taken together these data demonstrate that elevated lactate following PC suppression by hypoxia may be a key mechanism through which primary tumors limit antitumor immunity. Thus, these data highlight PC directed tumor metabolism is a nexus of tumor progression and antitumor immunity.

2023-12-29 | GSE199828 | GEO

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