Acetyl-CoA-carboxylase: modification of ATP-binding site of the active center by 2',3'-dialdehyde derivative of ATP

The interaction of rat liver acetyl-CoA carboxylase with a 2',3'-dialdehyde derivative of ATP (oATP) has been studied. The degree of the enzyme inactivation has been found to depend on the oATP concentration and the incubation time. ATP was the only reaction substrate which provided protection from inactivation. Acetyl-CoA did not affect inactivation, while HCO3- accelerated the process. Ki values for oATP in the absence and the presence of HCO3- were 0.35 +/- 0.04 and 0.5 +/- 0.06 mM, and those of the modification constant (k) were 0.11 and 0.26 min-1, respectively. oATP completely inhibited the reaction of 14C]ADP in equilibrium ATP exchange, whereas produced actually no effect on 14C]acetyl-CoA equilibrium with malonyl-CoA exchange. Incorporation of about one equivalent of 3H]oATP per acetyl-CoA carboxylase subunit has been shown. No restoration of the modified enzyme activity has been observed in Tris or beta-mercaptoethanol containing buffers, and treatment with NaB3H]4 has not led to 3H incorporation. The modification process involves elimination of the triphosphate chain of oATP. The results obtained indicate the affinity character of oATP-mediated modification of acetyl-CoA carboxylase. The reagent apparently interacts selectively with the epsilon-amino group of lysine in the ATP-binding site to form a morpholine-like structure.