Evidence for a Mixed Function Oxidase in the Biosynthesis of Ethanolamine Plasmalogens from 1-Alkyl-2-acyl-sn-glycero-3-phosphorylethanolamine

Our studies with 1-alkyl-2-acyl-sn-glycero-3-phosphoryl-ethanolamine and 1-akyl-sn-glycero-3-phosphorylethanol-amine, both labeled with 14C in the alkyl moiety, have shown that 1-alkyl-2-acyl-sn-glycero-3-phosphorylethanolamine is converted to 1-alk-1-enyl-2-acyl-sn-glycero-3-phosphoryl-ethanolamine (plasmalogen) by enzyme preparations from tumors. The conversion of the O-alkyl to O-alk-1-enyl linkage requires molecular oxygen and a reduced pyridine nucleotide (either NADH or NADPH) and is inhibited by cyanide, but not by carbon monoxide. The data implicate the involvement of a microsomal electron transport system that requires cytochrome b5 instead of P-450 in the biosynthesis of plasmalogens. These findings indicate that a microsomal mixed function oxidase, similar to the one required in the biosynthesis of monoenoic fatty acids, is involved in the biosynthesis of ethanolamine plasmalogens. ATP and Mg++ stimulated the synthesis of plasmalogens.