A continuation of our studies on the biosynthesis of fatty acids, cholesterol and carotenes is proposed. The emphasis in these studies will, however, be placed on the biosynthesis of fatty acids. In one area of study we will concentrate on the completion of immunotitrations of monospecific antibody with acetyl-CoA carboxylase and with fatty acid synthetase from livers of animals in different nutritional or hormonal states. Through these studies we will determine the ratio of active to inactive enzyme in livers of animals subjected to various experimental conditions. These studies will be followed by ones on the identification of the inactive species of these enzymes. We will also attempt to purify the transferase that converts apofatty acid synthetase to the holoenzyme to homogeneity and then determine the mechanism of its action. A second study will be concerned with the identity or nonidentity of the two subunits of the fatty acid synthetase and with the linear organization of activities on these subunits. These problems are being attacked through selective proteolysis of the enzyme complex, purification of the resultant protein products, antibody production to these proteins and immunotitration of the fatty acid synthetase with antibody that is monospecific to each of the protease cleavage products. These antiboies will also be used to prepare affinity columns for the attempted separation of the half-molecular weight subunits of the fatty acid synthetase complex. In another study we will attempt to purify the mRNA for the fatty acid synthetase to homogeneity. This mRNA will then be used to prepare cDNA for cloning. Studes on acetyl-CoA carboxylase will continue to concentrate on the mechanism of regulation of this enzyme by an inactivator (kinase) and an activator (phosphatase). Studies on the biosynthesis of cholesterol will be concerned with the mechanisms of regulation of HMG-CoA reductase activity and those on carotene biosynthesis will concentrate on the isolation and purification of enzymes that convert phytoene to acyclic and cyclic carotenes.