The interaction of mammalian medium-chain hydrolase with yeast fatty acid synthetase.

The interaction of rat mammary gland medium-chain thioesterase with yeast fatty acid synthetase has been investigated. Medium-chain thioesterase interacts with yeast fatty acid synthetase causing premature chain termination of the fatty acids synthesized from acetyl-CoA and malonyl-CoA. This effect is most marked under conditions of rate-limiting malonyl-CoA availability. Immobilized yeast fatty acid synthetase specifically binds rat mammary gland medium-chain thioesterase. This interaction has been used to purify medium-chain thioesterase to near homogeneity from samples of rat mammary gland cytosol. The stoichiometry of binding of medium-chain thioesterase to yeast fatty acid synthetase has been investigated. Yeast fatty acid synthetase binds 5.7 +/- 1 mol medium-chain thioesterase/mol yeast fatty acid synthetase. It is concluded that yeast fatty acid synthetase has a medium-chain thioesterase binding site.