Isolation, purification, and characterization of a peptide that contains the beta-ketoacyl reductase, enoyl reductase, and beta-hydroxyacyl dehydrase activities of the pigeon liver fatty acid synthetase.

Controlled proteolytic cleavage of pigeon liver fatty acid synthetase with elastase (4% w/w) for 5 h yields two peptides that are designated II and IV. After 5 h of proteolysis the incubation mixture containing these peptides retains all of the component enzyme activities of the fatty acid synthetase complex. The two peptides are then separated by chromatography on an Affi-Gel Blue column. Gel filtration of the fraction containing peptide II yields a homogeneous peptide as shown by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. The molecular weight of this peptide has been estimated to be 130 000 by sodium dodecyl sulfate--polyacrylamide gel electrophoresis, size exclusion chromatography, and amino acid analysis. The sedimentation coefficient for peptide II is approximately 7.4S. Peptide II contains the domains for the beta-ketoacyl and enoyl reductases and beta-hydroxyacyl dehydrase activities of the fatty acid synthetase complex.