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)

Carbonic anhydrase V (CA V) is expressed in mitochondrial matrix in liver and several other tissues. It is of interest for its putative roles in providing bicarbonate to carbamoyl phosphate synthetase for ureagenesis and to pyruvate carboxylase for gluconeogenesis and its possible importance in explaining certain inherited metabolic disorders with hyperammonemia and hypoglycemia. Following the recent characterization of the cDNA for human CA V, we report the isolation of the human gene from two lambda genomic libraries and its characterization. The CA V gene (CA5) is approximately 50 kb long and contains 7 exons and 6 introns. The exon-intron boundaries are found in positions identical to those determined for the previously described CA II, CA III, and CA VII genes. Like the CA VII gene, CA5 does not contain typical TATA and CAAT promoter elements in the 5' flanking region but does contain a TTTAA sequence 147 nucleotides upstream of the initiation codon. CA5 also contains a 12-bp GT-rich segment beginning 13 bp downstream of the polyadenylation signal in the 3' untranslated region of exon 7. FISH analysis allowed CA5 to be assigned to chromosome 16q24.3. An unprocessed pseudogene containing sequence homologous to exons 3-7 and introns 3-6 was also isolated and was assigned by FISH analysis to chromosome 16p11.2-p12.
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PMID:Genomic organization of the human gene (CA5) and pseudogene for mitochondrial carbonic anhydrase V and their localization to chromosomes 16q and 16p. 749 83

Carbonic anhydrase (CA) was examined in two adipocyte cell lines, 3T3-L1 and 3T3-F442A. Both CA III and non-CA III activities, measured by 18O mass spectrometry, were present in 3T3-L1 and 3T3-F442A adipocytes; however, no CA activity was detected in 3T3 preadipocytes of either line. These observations were supported by immunoblot experiments employing CA III and CA II isoform-specific antisera. CA III, a major protein in rodent and murine adipocytes, and CA II, another isoform known to be present in adipose tissue, were observed only in the differentiated 3T3 adipocytes. The differentiation-dependent expression of these isozymes may imply an adipocyte-related role for CA. Compared with cultures maintained in the absence of insulin, 3T3 adipocytes maintained in the presence of insulin exhibited 65-90% lower concentrations of CA III. CA II was unaffected. This negative effect of insulin on CA III may explain the metabolic regulation of adipose CA III observed in vivo. After media changes, 3T3 adipocyte cultures rapidly lower media pH, which in turn lowers the bicarbonate/CO2 of bicarbonate/CO2-buffered media. Cultures maintained at low pH displayed 50-90% lower concentrations of CA II and CA III. Similarly, cultures maintained in a low bicarbonate/CO2 media (GibCO2-I medium containing 1 mM bicarbonate under an atmosphere of 100% humidified air) displayed 30-50% lower CA II and CA III concentrations. Thus CA II and CA III concentrations are influenced by pH and bicarbonate/CO2. Neither effect, the pH or the GibCO2-I media effect, was associated with changes in the concentration of pyruvate carboxylase or ATP citrate lyase (2 markers of adipocyte differentiation). Because the regulation by pH and bicarbonate/CO2 may be relatively selective for CA in adipocytes, a simple method for reducing the concentration/activity of CA in 3T3 adipocytes is described that may be a useful tool for studies on the physiological role of the enzyme.
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PMID:Differentiation-dependent expression of carbonic anhydrase II and III in 3T3 adipocytes. 833 33

To investigate the mechanism by which HCO3- accelerates pyruvate metabolism in guinea pig liver mitochondria, we measured continuously, at pH 7.4 and 37 degrees C, 13C16O2 production from [1-13C]pyruvate by mass spectrometry and NADH concentration by fluorescence and analyzed total malate, citrate, and beta-hydroxybutyrate produced by standard biochemical methods. When [1-13C]pyruvate is added to the mitochondrial suspension, 13C16O2 concentration rises steeply in the first seconds and then slows to a steady lower rate. Carbonic anhydrase (CA) eliminates this initial phase, which shows that decarboxylation of pyruvate produces CO2, not HCO3-, and it does this more rapidly than it can equilibrate without CA. HCO3- (25 mM) increased 13C16O2 production, O2 consumption and total malate and citrate production and decreased NADH concentration and total beta-hydroxybutyrate production. After obtaining the total amount of 13C16O2, malate, citrate, and beta-hydroxybutyrate produced, we calculated that the addition of 25 mM HCO3- to the suspension medium increased the amount of pyruvate decarboxylated by pyruvate dehydrogenase (PDH) 16% and increased the amount carboxylated by pyruvate carboxylase 300%. This supports our initial proposal that HCO3- accelerates the pyruvate carboxylation, which in turn consumes ATP directly and NADH and acetyl CoA secondarily, all of which increase PDH activity. However, we found no acceleration of pyruvate decarboxylation by 0.5 and 1 microM free Ca2+ concentration, unless the mitochondria were uncoupled and ATP was added.
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PMID:Mechanism of the acceleration of CO2 production from pyruvate in liver mitochondria by HCO3-. 925 46

Carbonic anhydrase V (CA-V) is a mitochondrial enzyme that provides bicarbonate for pyruvate carboxylase in liver and kidney. In the course of a survey of the tissue distribution of CA-V, we detected intense immunostaining in pancreatic islets when sections from rat and mouse pancreases were reacted with a polyclonal antibody to recombinant mouse CA-V. The distribution and large number of CA-V-positive cells in each islet suggested that they represented beta cells. Double immunofluorescence staining of tissue sections and isolated islet cells showed cellular colocalization of CA-V and insulin, confirming that beta cells contain CA-V. Western blotting of rat islets of Langerhans and primary beta cells showed 33- and 30-kDa polypeptides of precursor and mature CA-V, respectively. The CA-V expression was beta cell-specific since no CA-V immunoreaction was detected in the primary alpha cells. Immunohistochemical staining for CA-I, CA-II, CA-IV, CA-VI, and CA-IX was negative in beta cells, and Western blotting of beta cells also failed to identify any CA in beta cells except CA-V. The specific localization of CA-V in beta cells led us to hypothesize that CA-V may be functionally linked to the regulation of insulin secretion. Consistent with this hypothesis, the CA inhibitor acetazolamide was found to be a strong inhibitor of glucose-stimulated insulin secretion by isolated rat pancreatic islets.
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PMID:Expression of carbonic anhydrase V in pancreatic beta cells suggests role for mitochondrial carbonic anhydrase in insulin secretion. 973 57

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