Three separate investigations are being carried out. One of these is concerned with studies relating to fatty acids, another to cholesterol, and the last to carotenes. Our studies on the biosynthesis of fatty acids are concerned with the structural organization and the mechanism of action of avian and mammalian liver fatty acid synthetases. In these studies we are attempting to dissociate fatty acid synthetase complexes to individual proteins and to determine the properties and the mechanism of the action catalyzed by each. We are also attempting to identify the factors that control the rates of synthesis and degradation of rat liver fatty acid synthetase and the mechanisms by which these controls are effected. Studies on the biosynthesis of cholesterol are concerned mainly with the purification of enzymes that effect the conversion of beta-hydroxy-beta-methylglutaryl-CoA to squalene and with the mechanisms of these reactions. These studies are also concerned with the identification of the factors that control the rate of synthesis of beta-hydroxy-beta-methylglutaryl-CoA reductase in mammalian liver. Studies on the biosynthesis of carotenes are concerned primarily with the isolation, purification and mechanism of action of the enzymes that effect the synthesis of these compounds.