{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,12]],"date-time":"2026-09-12T06:27:01Z","timestamp":1789194421096,"version":"build-2803163510"},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1978,3,1]]},"abstract":"<jats:p>1. Oxaloacetate synthesis catalysed by pyruvate carboxylase from a thermophilic Bacillus in the absence of acetyl-CoA required addition of high concentrations of pyruvate, MgATP2\u2212 and HCO3\u2212, and at 45\u00b0C occurred at a maximum rate approx. 20% of that in the presence of a saturating concentration of acetyl-CoA. The apparent Km for HCO3\u2212 at pH7.8 was 400mm without acetyl-CoA, and 16mm with a saturating activator concentration. The relationship between reciprocal initial rate and reciprocal MgATP2\u2212 concentration was non-linear (convex-down) in the absence of acetyl-CoA, but the extent of deviation decreased as the activator concentration was increased. The relationship between reciprocal initial rate and reciprocal pyruvate concentration was non-linear (convex-down) in the presence or absence of acetyl-CoA. 2. The optimum pH for catalysis of oxaloacetate synthesis was similar in the presence or absence of acetyl-CoA. The variation with pH of apparent Km for HCO3\u2212 implicated residue(s) with pKa 8.6 in catalysis of the activator-independent oxaloacetate synthesis. 3. Linear Arrhenius and van't Hoff plots were observed for the temperature-dependence of oxaloacetate synthesis in the absence of acetyl-CoA over the range 25\u201355\u00b0C. Ea (activation energy) was 56.3kJ\/mol and \u0394H\u2021 (HCO3\u2212) (enthalpy of activation) was \u221238.6kJ\/mol. In the presence of acetyl-CoA, biphasic Arrhenius and van't Hoff plots are observed with a change of slope at 30\u00b0C in each case. Ea was 43.7 and 106.3kJ\/mol above and below 30\u00b0C respectively. 4. Incubation of Bacillus pyruvate carboxylase with trinitrobenzenesulphonate caused specific inactivation of acetyl-CoA-dependent catalytic activity associated with the incorporation of 1.3\u00b10.2 trinitrophenyl residues per subunit. Activator-independent catalysis and regulatory inhibition by l-aspartate were unaffected. The rate of inactivation of acetyl-CoA-dependent catalysis by trinitrobenzenesulphonate was specifically decreased by addition of acetyl-CoA and other acetyl-CoA and other acyl-CoA species, but complete protection was not obtained. 5. All alkylacyl derivatives of CoA tested activated Bacillus pyruvate carboxylase; acetyl-CoA was the most effective. The apparent Ka exhibited a biphasic relationship with acyl-chain length for the straight-chain homologues. Certain long-chain acyl-CoA species showed additional activation at a high concentration. Weak activation occurred on addition of CoA or adenosine 3\u2032,5\u2032-bisphosphate, but carboxyacyl-CoA species and derivatives containing a modified phosphoadenosyl group were inhibitory. Thioesters of CoA with non-carboxylic acids, e.g. methanesulphonyl-CoA, serve as activators of the thermophilic Bacillus and Saccharomyces cerevisiae pyruvate carboxylases, but as inhibitors of pyruvate carboxylases obtained from chicken and rat liver. 6. \u03b1-Oxoglutarate mimics the effect of l-aspartate as a regulatory inhibitor of the pyruvate carboxylases from both the thermophilic Bacillus and Saccharomyces cerevisiae. l-Glutamate was ineffective in both cases.<\/jats:p>","DOI":"10.1042\/bj1690543","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T20:09:42Z","timestamp":1439237382000},"page":"543-558","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Pyruvate carboxylase from a thermophilic <i>Bacillus<\/i>. Studies on the specificity of activation by acyl derivatives of coenzyme A and on the properties of catalysis in the absence of activator"],"prefix":"10.1042","volume":"169","author":[{"given":"Susan M.","family":"Libor","sequence":"first","affiliation":[{"name":"Department of Biochemistry, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trichur K.","family":"Sundaram","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael C.","family":"Scrutton","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, University of London King's College, Strand, London WC2R 2LS, U.K."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/169\/3\/543\/569966\/bj1690543.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/169\/3\/543\/569966\/bj1690543.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,26]],"date-time":"2021-11-26T18:22:55Z","timestamp":1637950975000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/169\/3\/543\/12584\/Pyruvate-carboxylase-from-a-thermophilic-Bacillus"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1978,3,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1978,3,1]]}},"URL":"https:\/\/doi.org\/10.1042\/bj1690543","relation":{},"ISSN":["0264-6021"],"issn-type":[{"value":"0264-6021","type":"print"}],"subject":[],"published":{"date-parts":[[1978,3,1]]}}}