Properties of canine myocardial phosphatidylethanolamine N-acyltransferase.
Dog heart contains a membrane bound N-acyltransferase (transacylase) which transfers acyl groups from the sn-1 position of membrane phospholipids to the amino group of ethanolamine phospholipids in the presence of millimolar Ca2+ concentrations. Using crude membrane preparations, we found this N-acyltransferase activity to be heat sensitive and inhibited by sulfhydryl reagents. Pretreatment of a membrane fraction with trypsin reduced N-acyltransferase activity to 60% while pretreatment with trypsin and Triton X-100 together reduced it to 30% of the control value. At pH 8.0 both Sr2+ and Mn2+ could fully substitute for Ca2+ with respect to optimum ion concentration and molecular species of the product formed in dog heart membranes from endogenous substrates. Ba2+ was equally effective in achieving N-acylation of ethanolamine phospholipids while other divalent cations were less effective or ineffective. The reaction exhibited a pH optimum of 8.5 to 9.0 with both Ca2+ and Sr2+ while Mn2+ precipitated above pH 8.0 resulting in decreased N-acylation activity. Both phosphatidylcholine and 1-acyl lysophosphatidylcholine could serve as acyl donors. Triton X-100 at a concentration of 0.1% stimulated acyl transfer from exogenous phosphatidylcholine but inhibited acyl transfer from lysophosphatidylcholine.
D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D004285:Dogs; D005227:Fatty Acids / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D013379:Substrate Specificity; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013696:Temperature; D014357:Trypsin / Q000494:pharmacology
D005227:Fatty Acids; D010714:Phosphatidylethanolamines; D013439:Sulfhydryl Reagents; D000217:Acyltransferases; C042139:phosphatidylethanolamine N-acyltransferase; D014357:Trypsin