Title: Fatty acid-requiring mutant of Sac in acetyl-CoA carboxylase (structural gene mutation/multifunctional enzyme/ATP affinity a)
Abstract:The isolation and biochemical properties of a Saccharomyces cerevisiae mutant (accl-167) defective in acetyl-CoA carboxylase (acetyl-CoA:carbon-dioxide ligase (ADP forming), EC 6.4.1.2) activity are d...The isolation and biochemical properties of a Saccharomyces cerevisiae mutant (accl-167) defective in acetyl-CoA carboxylase (acetyl-CoA:carbon-dioxide ligase (ADP forming), EC 6.4.1.2) activity are described. The mutant is de- ficient in de novo biosynthesis of long-chain fatty acids and specifically requires a saturated fatty acid of chain length 14-16 C atoms for growth. Fatty acid synthetase levels were normal, but the acetyl-CoA carboxylase specific activity of the purified enzyme was reduced to approximately 5% compared to wild- type yeast. Upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis the purified mutant enzyme migrated as a single band and was essentially indistinguishable from the wild-type enzyme. The study of acetyl-CoA carboxylase partial activities revealed that the biotin incorporation capacity and the trans- carboxylase partial activity were unaffected whereas the biotin carboxylase compoilient enzyme,exhibited less than 10% of wild-type specific activity. This biotin carboxylase mutational deficiency could be ascribed to a more than 90% reduction of Vmax and to a comparable increase in the Km value for ATP, which was accompanied by an increased requirement for Mg2+. It is concluded that accl-167contains a structural gene mutation in the biotin carboxylase domain of acetyl-CoA carboxylase. The first step in the pathway of biosynthesis of long-chain fatty acids is the formation of malonyl-CoA catalyzed by acetyl-CoA carboxylase (acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2) (1). Overall acetyl-CoA carboxylation may be re- solved into two sequential reaction steps: biotin carboxylation and carboxybiotin-acetyl-CoA transcarboxylation (eqs. 1 and 2). Enzyme-biotin + HCOs + ATP Biotin carboxylaseRead More
Publication Year: 2016
Publication Date: 2016-01-01
Language: en
Type: article
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