Acylation of monolysocardiolipin in rat heart

Cardiolipin is a major mitochondrial membrane glycerophospholipid in the ma mmalian heart. In this study, the ability of the isolated intact rat heart to remodel cardiolipin and the mitochondrial enzyme activities that reacyla te monolysocardiolipin to cardiolipin in vitro were characterized. Adult ra t heart cardiolipin was found to contain primarily linoleic and oleic acids , Perfusion of the isolated intact rat heart in the Langendorff mode with v arious radioactive fatty acids, followed by analysis of radioactivity incor porated into cardiolipin and its immediate precursor phosphatidylglycerol, indicated that unsaturated fatty acids entered into cardiolipin mainly by d eacylation followed by reacylation. The in vitro mitochondrial acylation of monolysocardiolipin to cardiolipin was coenzyme A-dependent with a pH opti mum in the alkaline range, Significant activity was also present at physiol ogical pH, With oleoyl-coenzyme A as substrate, the apparent K-m for oleoyl -coenzyme A and monolysocardiolipin were 12.5 mu M and 138.9 mu M, respecti vely. With linoleoyl-coenzyme A as substrate, the apparent K-m, for linoleo yl-coenzyme A and monolysocardiolipin were 6.7 mu M and 59.9 mu M, respecti vely, Pre-incubation at 50 degrees C resulted in different profiles of enzy me inactivation for the two activities. Both activities were affected simil arly by phospholipids, triacsin C, and various lipid binding proteins but w ere affected differently by various detergents and myristoyl-coenzyme A. [H -3]cardiolipin was not formed from monolyso[H-3]cardiolipin in the absence of acyl-coenzyme A. Monolysocardiolipin acyltsansferase activities were obs erved in mitochondria prepared from various other rat tissues.jlr In summar y, the data suggest that the isolated intact rat heart has the ability to r apidly remodel cardiolipin and that rat heart mitochondria contain coenzyme A-dependent acyltransferase(s) for the acylation of monolysocardiolipin to cardiolipin, A simple and reproducible in vitro assay for the determinatio n of acyl-coenzyme A-dependent monolysocardiolipin acyltransferase activity in mammalian tissues with exogenous monolysocardiolipin substrate is also presented.