PURIFICATION AND CHARACTERIZATION OF ACETYL COA CARBOXYLASE FROM DEVELOPING PEA EMBRYOS

The aim of this work was to find out if the different lipid contents of the. embryos of round- and wrinkled-seeded peas (Pisum sativum L.) are related to differences in the properties or regulation of acetyl CoA carboxylase (EC 6.4.1.2) during embryo development. The enzyme was purified about 850-fold, to near-homogeneity, from developing embryos of both round- and wrinkled-seeded lines of peas. The properties of the enzyme from these two sorts of embryos are indistinguishable: the subunit size is 210 kD, and the K(m) values for acetyl CoA, bicarbonate and MgATP2- are 0.01-0.02 mM, 3.5 mM and 0.16 mM respectively. The enzyme from both sorts of embryo is strongly competitively inhibited by ADP and malonyl CoA, at concentrations likely to occur in the plastid. These metabolites may be important in the regulation of the activity of the enzyme, and hence of the flux of carbon into fatty acids, in vivo.