The Source of Oxygen in the Ether Bond of Glycerolipids

The reaction [see PDF for equation] is catalyzed by microsomal enzymes of preputial gland tumors. The data show that the oxygen of 18O-labeled hexadecanol is incorporated into O-alkyl lipids in vitro and in vivo. The experiment in vivo with Ehrlich ascites cells also revealed that the oxygen of the O-alk-1-enyl bond originates from the fatty alcohol. The most prominent peak showing the presence of 18O in the mass spectra of the acetates of the 18O-hexadecanol (94% 18O) used as the precursor was at m/e 61. [see PDF for equation] The isopropylidene derivatives of the biosynthetic 18O-hexadecylglycerol had a molecular peak at m/e 358 of low intensity, but removal of a methyl group by fragmentation produced resonance-stabilized oxonium ions containing 18O at m/e 343 of high intensity. Except for relative intensities, the hydrogenated 18O-hexadec-1-enylglycerol synthesized in vivo had a mass spectrum identical with that of the 18O-hexadecylglycerol produced in vitro or in vivo. The 18O content of the O-alkylglycerols biosynthesized was 89% (in vitro) and 34% (in vivo) and that of the O-alk-1-enylglycerol was 16% (in vivo).