Multiple cytosolic forms of hepatic β-hydroxy-β-methyglutaryl coA synthase: Possible regulatory role in cholesterol synthesis

Abstract

Summary Two cytosolic forms (I and II) of HMG CoA synthase have been obtained in homogeneous form from chicken liver. The two enzymes have distinctly different electrophoretic and chromatographic properties; synthase I is composed of a single polypeptide chain of about 52,000 daltons, whereas, two identical or similar polypeptide chains of about 55,000 daltons comprise synthase II. On the basis of their cytoplasmic localization and the fact that cholesterol feeding has a negative feed-back effect on cytosolic synthase activity, it appears that one or both of these enzymes carry out the committed step in hepatic cholesterol synthesis.