N-acylation of ethanolamine phospholipids in canine myocardium

Abstract

N-Acylethanolamine phospholipids, which are found in infarcted but not in normal canine myocardium, were produced by preparations of normal myocardial tissue incubated in the presence of millimiolar concentrations of Ca 2+. Biosynthetic activity from endogenous substrates was associated with both microsomal and mitochondrial fractions and exhibited an alkaline pH optimum. The time course of N-acylethanolamine phospholipid synthesis and degradation was followed after pulse labeling of myocardial ethanolamine phospholipids with [1,2- 14C]ethanolamine. Enzymic N-acylation of both phosphatidylethanolamine and lysophosphatidylethanolamine was demonstrated by incubating these substrates with homogenates of myocardial tissue. Neither free fatty acids nor acyl-CoA derivatives served as acyi donor but some of the constituent fatty acids of exogenous phosphatidylethanolamine were recovered among the amide-linked fatty acids of the N-acylethanolainine phospholipids. N-Acylation may thus occur by the transfer of O-acyl groups catalyzed by a Ca 2+-dependent transacylase. Since N-acylethanolamine phospholipids are precursors of the biologically active N-acylethanolamines, their biosynthesis may constitute an important injury-induced metabolic event aimed at the protection of ischwmic myocardial tissue.