Phosphorylation by cyclic AMP‐dependent protein kinase does not affect the association of ATP citrate‐lyase with isolated mitochondria

Abstract

ATP citrate‐lyase is known to be a substrate for various protein kinases, but the functional role, if any, of kinase‐directed phosphorylation of this enzyme has not been identified. Recently, Strålfors [(1987) J. Biol. Chem. 262, 11486–11489] has suggested that effects on the association of this enzyme with mitochondria may account for the observed ability of isoproteronol or insulin to promote immobilization of ATP citrate‐lyase in permeabilized cells. Here we report studies involving phosphorylation of the pure enzyme in vitro using cyclic AMP‐dependent protein kinase. We show that phosphorylation has no significant effect on the fraction of the enzyme that may be bound to isolated mitochondria.