Acylation of monolysocardiolipin in rat heart

Vernon W. Dolinsky,Grant M. Hatch,William A. Taylor,Brian J. Ma

doi:10.1016/s0022-2275(20)34900-2

Abstract

Cardiolipin is a major mitochondrial membrane glycerophospholipid in the mammalian heart. In this study, the ability of the isolated intact rat heart to remodel cardiolipin and the mitochondrial enzyme activities that reacylate monolysocardiolipin to cardiolipin in vitro were characterized. Adult rat heart cardiolipin was found to contain primarily linoleic and oleic acids. Perfusion of the isolated intact rat heart in the Langendorff mode with various radioactive fatty acids, followed by analysis of radioactivity incorporated into cardiolipin and its immediate precursor phosphatidylglycerol, indicated that unsaturated fatty acids entered into cardiolipin mainly by deacylation followed by reacylation. The in vitro mitochondrial acylation of monolysocardiolipin to cardiolipin was coenzyme A-dependent with a pH optimum in the alkaline range. Significant activity was also present at physiological pH. With oleoyl-coenzyme A as substrate, the apparent K(m) for oleoyl-coenzyme A and monolysocardiolipin were 12.5 microm and 138.9 microm, respectively. With linoleoyl-coenzyme A as substrate, the apparent K(m) for linoleoyl-coenzyme A and monolysocardiolipin were 6.7 microm and 59.9 microm, respectively. Pre-incubation at 50 degrees C resulted in different profiles of enzyme inactivation for the two activities. Both activities were affected similarly by phospholipids, triacsin C, and various lipid binding proteins but were affected differently by various detergents and myristoyl-coenzyme A. [(3)H]cardiolipin was not formed from monolyso[(3)H]cardiolipin in the absence of acyl-coenzyme A. Monolysocardiolipin acyltransferase activities were observed in mitochondria prepared from various other rat tissues. In summary, the data suggest that the isolated intact rat heart has the ability to rapidly 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 determination of acyl-coenzyme A- dependent monolysocardiolipin acyltransferase activity in mammalian tissues with exogenous monolysocardiolipin substrate is also presented.

Highlights

Cardiolipin is a major mitochondrial membrane glycerophospholipid in the mammalian heart
To examine whether the isolated intact rat heart could reacylate MLCL to CL, we initially examined the molecular composition of CL and its immediate precursor PG in rat heart
Because saturated fatty acids such as palmitic acid enter into glycerophospholipids mainly by glycerophospholipid de novo biosynthetic pathways [38], the data suggest that cardiac CL is remodeled to obtain its appropriate molecular composition in vivo

Summary

Introduction

Cardiolipin is a major mitochondrial membrane glycerophospholipid in the mammalian heart. The ability of the isolated intact rat heart to remodel cardiolipin and the mitochondrial enzyme activities that reacylate monolysocardiolipin to cardiolipin in vitro were characterized. The in vitro mitochondrial acylation of monolysocardiolipin to cardiolipin was coenzyme A-dependent with a pH optimum in the alkaline range. The data suggest that the isolated intact rat heart has the ability to rapidly 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 determination of acyl-coenzyme A-dependent monolysocardiolipin acyltransferase activity in mammalian tissues with exogenous monolysocardiolipin substrate is presented.—Ma, B.

Objectives

Methods

Results

Conclusion