Formation of palmityl-[3′- 32P]coenzyme a from [γ- 32P]ATP in mitochondrial extracts of guinea pig liver

Abstract

Investigations of the incorporation of 32P into acyl-coenzyme A (CoA) in incubation mixtures containing a soluble protein preparation derived from mitochondria, [γ- 32P]ATP, and palmityl-CoA have led to the discovery of an enzymatic activity which catalyzes the exchange of palmityl groups between molecules of CoA: CoA ∗ + palmityl-CoA ↔ palmityl-CoA ∗ + CoA. The preparation also contains dephospho-CoA kinase and palmityl-CoA thiolester hydrolase activities. The initial detection of the exchange reaction resulted from the formation of [3′- 32P]CoA via the dephospho-CoA kinase reaction with exogenous [γ- 32P]ATP. The described preparation of palmityl-[3′- 32P]CoA and palmityl-[ 35S]CoA facilitated demonstration of the reversibility of the reaction and ruled out the possibility that the exchange of fragments of the CoA molecule mediated the observed incorporation. The reversible palmityl group exchange does not appear to be catalyzed by a previously described enzyme. None of the possible acyl group acceptors considered in these studies participated in the reaction as efficiently as CoA itself. The possibility is discussed that the exchange reaction may explain reports of an unknown lipid formed by an oligomycin-sensitive mitochondrial ATPase preparation.