ISOLATION AND CHARACTERIZATION OF ACETYL-COA SYNTHETASE FROM ETIOLATED RADISH SEEDLINGS

Acetyl-CoA synthetase (ACS; E.C. 6.2. 1. 1.) is a key enzyme in plasti ds of higher plants which provides the starting substrate acetyl-CoA f or de novo fatty acid biosynthesis. The ACS enzyme activities, measure d in leaves and chloroplasts of different plants, are described. The e nzyme was purified 183-fold from etiolated radish cotyledons to a fina l specific activity of 193 nmol min-1 mg-1 protein. The properties, th e substrate specifity and the Michaelis-Menten constants (K(m) for ATP , acetate and coenzyme A) of the purified enzyme were determined. The ACS exhibits a high substrate specifity for acetate as compared to oth er organic acids (e.g. propionic, acrylic or butyric acid).