CRITICAL PHOSPHORYLATION SITES FOR ACETYL-COA CARBOXYLASE ACTIVITY

Acetyl CoA carboxylase (ACC) is rapidly regulated by reversible phosph orylation; phosphorylation inactivates ACC, whereas dephosphorylation activates the enzyme. Among protein kinases only cAMP-dependent protei n kinase and 5'-AMP-dependent protein kinase can inactivate ACC; cAMP- dependent protein kinase phosphorylates Ser-77 and -1200; 5'-AMP-depen dent protein kinase phosphorylates Ser-79, -1200, and -1215. In this r eport, the construction and expression of ACC cDNA containing the enti re coding region (7.2 kilobase pairs) is described. In order to identi fy the critical phosphorylation site(s) for each protein kinase, we in troduced site-specific mutations at Ser-77, -79, -1200, and -1215 of A CC cDNA and a series of mutated ACCs containing various combinations o f these four mutated sites was expressed. By examination of the variou s mutant ACCs, we provided evidence that the effect of cAMP-dependent protein kinase is entirely mediated by the phosphorylation of Ser-1200 and that Ser-79 is important for 5'-AMP-dependent protein kinase acti on in vitro.