Fatty Acid Synthetase of Chicken Liver: A Novel Active-Site Structure for Condensation Comprised of SH Groups from a Cysteine Residue and an Oscillating Phosphopantetheine Swinging Arm on Adjacent Subunits

Abstract

The synthesis of palmitic acid by avian fatty acid synthetase occurs through successive elongation of the acetyl primer by two-carbon acyl residues from malonyl-CoA, and reduction of the resulting ketoacyl intermediates by NADPH to corresponding saturated acyl derivatives. After completion of seven elongation cycles, enzyme-bound palmitate is released as the free acid. The enzyme complex is a dimeric molecule comprised of identical subunits. Each subunit contains, in addition to active sites for component reactions, a phosphopantetheine SH group which serves as a carrier for the covalently attached acyl intermediates (1).