The enzymic synthesis of ethanolamine plasmalogens.

Enzymic synthesis of ethanolamine plasmalogens from l-14C-hexadecanol in cell-free systems from Ehrlich ascites and Freputial gland tumors of mice is documented. Identiiication of the ethanolamine plasmalogens is based on the preparation and chromatographic behavior of a number of chemical derivatives that take into account all three positions on the glycerol moiety. 14C-Derivatives isolated from intact ethanolamine plasmalogens included (a) hexadecanal liberated by aq,ueous HCI, (b) dimethylacetals of hexadecanal formed by HCl-methanol treatment, (c) 0-alk-1 -enylglycerols liberated by reduction with LiA1H4 or NaAlH2(0CH2CH2. OCHJ2, (d) 0-alkylglycerols obtained by hydrogenation of 0-alk1 -enylglycerols, (e) isopropylidene derivatives of the hydrogenated 0-alk-1-enylglycerols, (f) lysoethanolamine plasmalogens after phospholipase A treatment, and (g) dinitrobenzene derivatives of the intact ethanolamine plasmalogens. NaA1H2(0CH2CH20CH,)2, a new reagent that we used for the reduction of ether-linked glycerolipids, gives better yields of 0-alk-l-enylglycerols than LiA1H4. The system used for plasmalogen biosynthesis contained fatty alcohol, dihydroxyacetone phosphate, ATP, coenzyme A, Mg++, NADP+ or NAD+, microsomes, and the soluble fraction from tumors. Soluble fraction from rat liver can replace the soluble fraction from tumors. Data obtained with U-I%!-labeled dihydroxyacetone phosphate and 9, 10-3H-hexadecanol demonstrated that the aH:14C ratios in O-alkylglycer01s and 0-alk-1-enylglycerols (isolated after LiA1H4reduction) were essentially identical. lJ4C-Palmitic acid was not incorporated into the 0-alk-I-enyl moiety and added unlabeled hexadecanal had little effect on plasmalogen biosynthesis. These data, along with the substrate and cofactor requirements, suggest that an 0-alkyl glycerolipid was converted to an ethanolamine plasmalogen.