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)

At 37 degrees C, pH 7.4, carbonic anhydrase activity (kenz) of disrupted rat renal proximal tubules and cortical mitochondria was 2.5 +/- 0.8 (n = 3) and 0.15 +/- 0.40 (n = 3) ml.mg-1.s-1, respectively. Turnover number for renal mitochondrial carbonic anhydrase (CA V) was 24,000 s-1. CA V activity of intact mitochondria was completely inhibited by 0.15 microM ethoxzolamide (EZ). Intact proximal tubules, prepared from 48-h starved male rats, were incubated at 37 degrees C in 10 mM pyruvate in Krebs-Henseleit bicarbonate saline buffer, 5% CO2-95% O2. The rate of glucose synthesis over 60 min was reduced 50% by including 0.6 microM EZ in the incubation solution. The concentration of NaHCO3 was doubled to 50 mM (with a corresponding decrease in NaCl) and the solution gassed with 10% CO2-90% O2; 2.4 microM EZ no longer decreased glucose synthesis. It was concluded that inhibition of glucose synthesis by EZ was directly a result of inhibiting the carbonic anhydrases. The rate of glucose production was subsequently determined with tubules incubating in a HCO3(-)-free N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES) buffer; this rate was decreased 50% by 0.6 microM EZ. These data support the hypotheses that CA V provides HCO3- for pyruvate carboxylase and that CO2 can be provided by tubular metabolism. Intact tubules were incubated in from 5 to 20 mM pyruvate in either 25 or 50 mM HCO3-; in either buffer, the rate of glucose synthesis was similar, increasing with increasing pyruvate concentration. At no pyruvate concentration was there a change in the rate of glucose production when tubules were incubated in 50 mM HCO3- buffer with 1.6 microM EZ. These data also support the hypothesis that CA V provides the HCO3- substrate for pyruvate carboxylation when there is a high rate of intracellular CO2 production and external CO2 is low. It is further concluded that the cytosolic carbonic anhydrase (CA II) and the membrane-bound carbonic anhydrase (CA IV) are not involved in glucose synthesis from pyruvate.
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PMID:Mitochondrial carbonic anhydrase is involved in rat renal glucose synthesis. 251 97

In peripheral tissues, carbonic anhydrase (CA) inhibition secondarily decreases the anaplerotic activity of pyruvate carboxylase activity leading to a decline in citric acid cycle intermediates and glutamate. In view of the important role of pyruvate carboxylase in the brain, we examined the effects of CA inhibition on pyruvate-carboxylase-mediated [14C]CO2 fixation in cultured astrocytes from postnatal rat brains. Incubation with H[14C]O3 led to radiolabeling of metabolites found both in the cells and in the medium. These were separated by ion exchange chromatography for identification. Ethoxyzolamide (ETZ), a sulfonamide CA inhibitor (SCAI) with a heterocyclic side group, caused a 43-73% decrease in cell lysate [alpha-ketoglutarate] and 14C incorporation into major products of pyruvate carboxylation in the cell lysates and cell medium (i.e., released products). Half-maximal inhibition of [14C]CO2 fixation was observed between 1 and 3 x 10(7) M. This is similar to the IC50 value for ETZ inhibition of events in other cells that are thought to be mediated by CA. Inhibition was also observed with trifluormethanesulfonamide, an aliphatic SCAI, providing further evidence that this effect is mediated by CA. Western blot analysis using isozyme-specific antisera indicated that astrocytes contain CA II, a cytosolic isozyme, but CA III, CA IV and CA V could not be detected. This finding is unusual since the effects of SCAIs on pyruvate carboxylation in other tissues have been attributed to inhibition of the intramitochondrial isozyme. CA V. [14C]CO2 fixation was also decreased by lowering media [pyruvate] or by addition of 5 mM acetoacetate. It is hypothesized that SCAIs may inhibit pyruvate carboxylation in astrocytes by limiting the supply of bicarbonate to this enzyme while ketone bodies, by inhibiting glucose oxidation, may limit the supply of pyruvate. Interestingly, both SCAIs and ketogenic diets are used to treat adolescent forms of epilepsy. The possibility that these treatments might ultimately work by affecting anaplerotic pyruvate carboxylase activity in the brain is discussed.
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PMID:Effect of carbonic anhydrase inhibition and acetoacetate on anaplerotic pyruvate carboxylase activity in cultured rat astrocytes. 909 31

Carbonic anhydrase (CA) V is a mitochondrial enzyme that has been reported in several tissues of the gastrointestinal tract. In liver, it participates in ureagenesis and gluconeogenesis by providing bicarbonate ions for two other mitochondrial enzymes: carbamyl phosphate synthetase I and pyruvate carboxylase. This study presents evidence of immunohistochemical localization of CA V in the rodent nervous tissue. Polyclonal rabbit antisera against a polypeptide of 17 C-terminal amino acids of rat CA V and against purified recombinant mouse isozyme were used in western blotting and immunoperoxidase stainings. Immunohistochemistry showed that CA V is expressed in astrocytes and neurons but not in oligodendrocytes, which are rich in CA II, or capillary endothelial cells, which express CA IV on their plasma face. The specificity of the immunohistochemical results was confirmed by western blotting, which identified a major 30-kDa polypeptide band of CA V in mouse cerebral cortex, hippocampus, cerebellum, spinal cord, and sciatic nerve. The expression of CA V in astrocytes and neurons suggests that this isozyme has a cell-specific, physiological role in the nervous system. In astrocytes, CA V may play an important role in gluconeogenesis by providing bicarbonate ions for the pyruvate carboxylase. The neuronal CA V could be involved in the regulation of the intramitochondrial calcium level, thus contributing to the stability of the intracellular calcium concentration. CA V may also participate in bicarbonate ion-induced GABA responses by regulating the bicarbonate homeostasis in neurons, and its inhibition could be the basis of some neurotropic effects of carbonic anhydrase inhibitors.
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PMID:Mitochondrial carbonic anhydrase in the nervous system: expression in neuronal and glial cells. 1103 10