The fatty acid synthetase of pigeon liver catalyzes the conversion of acetyl-and malonyl-coenzyme A to long chain saturated fatty acids in the presence of reduced nicotinamide adenine dinucleotide phosphate. The major product of the reaction is palmitic acid, but small amounts of other long chain fatty acids are also formed.

The over-all reaction for the synthesis of palmitic acid is: 1 acetyl-CoA+ 7 malonyl-CoA+ 14 NADPH+ 14 H++ 1 palmitic acid+ 14 NADP++ 7 COz+ 8 CoA+ 6 Hz0 (1). Acetyl-CoA serves as a primer for the reaction, and it is incorporated into the methyl end of the palmitic acid (2). The synthesis of palmitic acid is achieved through the formation of a series of intermediates covalently bound to protein (3-5). In this process, acetyl-enzyme is condensed with malonyl-enzyme to yield acetoacetyl-enzyme with the concomitant release of COZ. Acetoacetyl-enzyme is then reduced, dehydrated, and again reduced to butyryl-enzyme. The condensation, reduction, and dehydration reactions are repeated seven times, and each time a 2-carbon unit from malonyl-CoA is added to the intermediate acyl-enzyme compound. The formation of P-hydroxy-fl-methylglutaryl coenzyme A, 3, 5-diketohexanoic acid, and mevalonic acid is also effected by the partially purified pigeon liver fatty acid synthetase (3, 6). The pigeon liver enzyme was purified by Bressler and Wakil (1) to an activity of 0.3 pmole of NADPH oxidized per min per mg of protein. The integrity of this enzyme system was not established, however.