Stimulated neutrophils produce an ethanolamine plasmalogen analog of platelet-activating factor.
Human neutrophils stimulated by ionophore A23187 incorporate [3H]acetate into platelet-activating factor and an additional product which is chromatographically similar to phosphatidylethanolamine and accounts for approximately 25% of the [3H]acetate-containing lipids. Three general approaches indicated the sn-1 moiety of the unknown phospholipid is primarily alk-1'-enyl-linked: 1) approximately 80% of the intact phospholipid as well as its derivatives was highly sensitive to hydrolysis by HCl, 2) 80% of the product which resulted from treating the unknown with phospholipase C and acetylating the free hydroxyl group at the sn-3 position, chromatographed with authentic 1-O-alk-1'-enyl-2,3-diacetylglycerol, and 3) catalytic hydrogenation of the diacetylglycerol product described in 2) resulted in a product which chromatographed with alkyldiacetylglycerol and was not sensitive to strong acid. Treatment of the intact phospholipid with phospholipase A2 resulted in the release of 88% of the radiolabel into the acidified aqueous phase of the extraction mixture, indicating the moiety in the sn-2 position remained as acetate and had not been elongated to fatty acid. The head group was determined to be phosphoethanolamine based upon its complete conversion to the dinitro- and trinitrophenyl derivatives by the amine-derivatizing reagents fluorodinitrobenzene and trinitrobenzenesulfonic acid, respectively. From these data is was concluded that the unknown product is 1-O-alk-1'-enyl-2-acetyl-sn-glycero-3-phosphoethanolamine (80%), and 1-O-alkyl-2-acetyl-sn-glycero-3-phosphoethanolamine (10%). Sonicates prepared from neutrophils stimulated with ionophore A23187 contained an acetyltransferase activity capable of utilizing 1-O-alk-1'-enyl-2-lyso-sn-glycero-3-phosphoethanolamine and [14C]acetyl-CoA to produce the product identified as 1-O-alk-1'-enyl-2-acetyl-sn-glycero-3-phosphoethanolamine.
D000107:Acetylation; D000001:Calcimycin / Q000494:pharmacology*; D002855:Chromatography, Thin Layer; D006801:Humans; D006868:Hydrolysis; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010741:Phospholipases A / Q000494:pharmacology; D054467:Phospholipases A2; D010955:Plasmalogens / Q000096:biosynthesis* / Q000302:isolation & purification; D012269:Ribosomal Proteins / Q000032:analysis*
D010955:Plasmalogens; C053634:RPL7 protein, human; D012269:Ribosomal Proteins; C020791:phosphatidal ethanolamines; D000001:Calcimycin; D010741:Phospholipases A; D054467:Phospholipases A2