THE ACTIVITIES OF ACYL-COA HYDROLASE IN LYSATE AND SUBCELLULAR-FRACTIONS OF HUMAN BLOOD-PLATELETS IN RELATION TO ACTIVITIES OF ACYL-COA-1-ACYL-LYSOPHOSPHOLIPID ACYLTRANSFERASE

The activities of acyl-CoA hydrolase (EC 3.1.2.2.) and acyl-CoA:1-acyl -lysophospholipid acyltransferase (EC 2.3.1.23) have been studied in s ubcellular fractions of human platelets. The acyl-CoA:1-acyl-lysophosp holipid acyltransferase activity was higher in the 'dense-tubular-syst em-enriched' fraction than in the 'light-mitochondrial' fraction, usin g endogenously acyl-CoAs formed from labelled fatty acids, ATP, CoA an d various lysophospholipids. No activity was found in the 'particle-fr ee' fraction. No difference in specificities was observed between the incorporation of various fatty acids into different lysoPLs in the sub cellular fractions compared with the platelet lysates. Generally, arac hidonic, linoleic and eicosapentaenoic acids were better substrates fo r the acyl-CoA:1-acyl-lysophospholipid acyltransferases than oleic, do cosahexaenoic and palmitic acids. The opposite was observed with the a cyl-CoA hydrolase activity, palmitoyl-CoA was the substrate giving the highest activity, and eicosapentaenoyl-CoA and arachidonoyl-CoA the l owest. About 85% of the hydrolase activity was detected in the 'partic le-free' fraction, with each of the six acyl-CoA derivatives tested.