Yeast mutants defective in acetyl-coenzyme A carboxylase and biotin: apocarboxylase ligase

Eur J Biochem. 1980 Oct;111(1):79-87. doi: 10.1111/j.1432-1033.1980.tb06077.x.


Among more than 7000 mutants of Saccharomyces cerevisiae, requiring saturated fatty acids, 61 acetyl-CoA-carboxylase-deficient strains have been identified. According to their mutual complementation characteristics these mutants have been assigned to two different genes, acc1 and acc2. Both acetyl-CoA carboxylase genes are unlinked to each other and to the fatty acids synthetase genes fas1 and fas2. The acetyl-CoA carboxylases of several acc1 and acc2 mutants have been purified and assayed for their overall and component enzyme activities. Besides overall acetyl-CoA carboxylation, which was lost in all cases, both component enzymes, biotin carboxylase and transcarboxylase, were simultaneously affected in most mutants, though often to a different relative extent. Similarly, the comparison of biochemical and genetic complementation data revealed no basis for a clear distinction between specific biotin carboxylase and transcarboxylase mutants. These results suggest that acc1 is a cluster gene coding for a multifunctional protein harboring both acetyl-CoA carboxylase component enzyme activities on the same polypeptide chain. The acetyl-CoA carboxylase isolated from acc2 mutants was free of biotin. Correspondingly, biotin:apoacetyl-CoA-carboxylase ligase activity was missing in acc2 mutants. Therefore, it is concluced that the primary defect in acc2 mutants is in the biotin:apocarboxylase ligase. In agreement with this conclusion, the acc2 acetyl-CoA carboxylase can be activated, in the presence of biotin and ATP, by ligase preparations from wild-type or acc1 mutant cells. By the use of these mutants, evidence was obtained that in vivo the biotinylation of both acetyl-CoA carboxylase and pyruvate carboxylase is catalyzed by the same ligase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyl-CoA Carboxylase / genetics*
  • Carbon-Nitrogen Ligases*
  • Genetic Complementation Test
  • Ligases / genetics*
  • Mutation
  • Saccharomyces cerevisiae / enzymology*
  • Species Specificity


  • Ligases
  • Carbon-Nitrogen Ligases
  • biotin-(acetyl-CoA carboxylase)synthetase
  • Acetyl-CoA Carboxylase