Evidence that acyl coenzyme A synthetase activity is required for repression of yeast acetyl coenzyme A carboxylase by exogenous fatty acids.

The cellular content of acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] in Saccharomyces cerevisiae is reduced by the addition of long-chain fatty acids to the culture medium. Mutant strains of S. cerevisiae defective in acyl-CoA synthetase [acid:CoA ligase (AMP-forming), EC 6.2.1.3] were isolated and used to determine whether fatty acid itself or a metabolite of fatty acid is more directly responsible for the repression of acetyl-CoA carboxylase. Cells of the mutant strains were capable of incorporating fatty acid to an extent comparable to that observed with the wild-type strain, but they accumulated markedly more of the incorporated fatty acid in the nonesterified form than did the wild-type cells. The level of acetyl-CoA carboxylase activity in the mutants, in contrast to that in the wild-type strain, was hardly affected by the addition of fatty acids to the medium. These results indicate that the activation of exogenous fatty acid is required for the repression of acetyl-CoA carboxylase, supporting the view that the repressive effect is mediated by some compound metabolically derived from fatty acid.