Plasmalogen biosynthesis in Madin-Darby canine kidney cells: Selectivity in the acylation of 1-alkyl-2-lyso-sn-glycero-3-phosphoethanolamine and the subsequent desaturation step

Abstract Acyl group specificity in the acylation of 1-alkyl-2-lyso- sn -glycero-3-phosphoethanolamine (1-alkyl-2-lyso-GroPEtn) to form 1-alkyl-2-acyl- sn -glycero-3-phosphoethanolamine (1-alkyl-2-acyl-GroPEtn) and the subsequent desaturation of 1-alkyl-2-acyl-GroPEtn to form plasmalogens (1-alk-1′-enyl-2-acyl- sn -glycero-3-phosphoethanolamine, i.e., 1-alk-1′-enyl-2-acyl-GroPEtn) was investigated in intact Madin-Darby canine kidney (MDCK) cells and cell-free membrane preparations. We found 1-[ 3 H]alkyl-2-lyso-GroPEtn was selectively acylated with polyunsaturated fatty acids in the order 20:4 > 20:5 > 20:3 ( n -9) > 22:6 by cell-free membrane preparations of MDCK cells. The same pattern of acyl specificity was seen in intact MDCK cells, although the intact cells produced significantly larger amounts of 1-[ 3 H]alkyl-2-acyl-GroPEtn containing oleic acid. There was an increased desaturation of the 1-[ 3 H]alkyl-2-acyl-GroPEtn species containing docosahexaenoic acid to plasmalogens (1-[ 3 H]alk-1′-enyl-2-acyl-GroPEtn) by both intact MDCK cells and the cell-free membrane preparations. The relatively rapid disappearance of the 1-[ 3 H]alk-1′-enyl-2-docosahexaenoyl-GroPEtn species during a 20-h incubation of prelabeled intact MDCK cells suggests a more rapid turnover of this molecular species. Our results indicate there is a high selectivity in the final acylation and desaturation steps of the biosynthetic pathway for plasmalogens.