Substrate specificity in plasmalogen biosynthesis. Desaturation of...

1-O-[1'-14C]Hexadecyloxyethyl rac-glycerol was administered to 18-day-old rats by intracerebral injection, and incorporation of radioactivity into the brain lipids was determined after 6, 24 and 48 h. Some of the substrate was catabolized by oxidative cleavage of either of the two ether bonds. Cleavage in the hexadecyloxyethyl moiety yielded labeled palmitic acid, whereas oxidative cleaveage of the glycol glycerol ether bond produced O-hexadecyl glycolic acid. The substrate was also incorporated as such into both ethanolamine and choline phospholipids. Evidence is presented for the desaturation by rat brain of 1-O-hexadecyloxyethyl-2-acyl-sn-glycero-3-phosphoethanolamine to the plasmalogen analogue, while the corresponding choline phospholipid was not desaturated.