Relative Activities of Acetyl-CoA Carboxylase and Fatty Acid Synthetase in Chick Liver: Effects of Dietary Fat

Abstract

The specific activities of acetyl-CoA carboxylase and fatty acid synthetase were measured in the cytosol fraction of livers from chicks fed various levels of corn oil, cottonseed oil, corn-oil free fatty acids, or crude (79%) oleic acid. Activities of both enzymes were depressed by the addition of fat to a fat-free basal diet. The ratios of synthetase to carboxylase activity were greater than unity when up to 4% fat was fed, but less than unity when 8% or higher levels of fat were fed. The depressions of the activities of these enzymes appeared to be unrelated to the dietary level of linoleate. In in vitro experiments, 2 μM concentrations of palmityl-CoA or oleoyl-CoA depressed acetyl-CoA carboxylase activity. Concentrations of 20 μM of these acyl-CoA esters did not affect the activity of fatty acid synthetase.