Fatty acid biosynthesis in yeast

Summary Fatty acid synthetase and acetyl CoA carboxylase mutants have been used to study several aspects of fatty acid biosynthesis in yeast: the contribution of the various enzymes of fatty acid biosynthesis and modification to the overall cellular fatty acid composition, the mechanism of fatty acyl chain elongation in yeast, the molecular structure and the reaction mechanism of the fatty acid synthetase complex and the genetic control of the biosynthesis of this multi-enzyme system. Genetic and biochemical evidence suggest an ₆₆ molecular structure of this complex, where and are multifunctional proteins comprising, respectively, 3 and 5 of the various fatty acid synthetase component functions. The two subunits and are synthesized on two different, unliked genes, fas 2 and fas 1. The biosynthesis of both is coordinated. The various component enzyme activities reside in distinct domains on the multifunctional chains. While most domains appear to be functionally independent, the three acyl transferases exhibit extensive mutual interactions. It is suggested that the biosynthesis of a multifunctional protein is favoured on the grounds of kinetics and regulation as compared with the formation of a complex of the corresponding individual enzymes.