Mammalian Fatty Acid Synthetase. I. Purification and Properties of Human Liver Complex

Abstract

The human liver fatty acid synthetase complex was obtained in highly purified form as judged by agarose gel filtration chromatography, analytical ultracentrifugation, and polyacrylamide disc gel electrophoresis. On the basis of sedimentation equilibrium, its molecular weight was computed to be 410 000 ± 20 000. The major product was palmitic acid. One mole of the prosthetic group, 4′-phosphopantetheine, was present per mole of synthetase.Both acetyl-CoA and butyryl-CoA were effective primers of fatty acid synthesis. Under appropriate conditions, the intermediates, acetyl – and malonyl – fatty acid synthetase could be isolated. On the basis of pretreatment of the synthetase with N-ethylmaleimide and exposure of the intermediates to performic acid, it was determined that the complex had both thiol and non-thiol acyl-binding sites. The available evidence indicates that the mechanism of fatty acid synthesis is analogous to that previously described for the yeast and avian synthetases.