| Abstract: | Rat liver microsomes labeled with spin-labeled phosphatidylcholine release the label into the aqueous phase during the aerobic incubation with NADPH (Biochem. Biophys. Res. Commun. (1979) 87, 300-307). To establish the chemical nature of the released moiety, microsomes were labeled with 14C]phosphatidylcholine. When the 14C-labeled microsomes were incubated with NADPH under aerobic conditions, a few percent of the radioactivity was liberated into the aqueous phase within 60 min. Thin-layer chromatographic analysis of the radioactive substance liberated showed the presence of hydroxylated fatty acids derived from the 2-position of glycerol moiety. About one-third of the fatty acids formed from 14C]phosphatidylcholine during the incubation were converted into hydroxy-derivatives. Gas chromatography/mass spectrometry analysis further confirmed an NADPH-dependent formation of 16-hydroxypalmitic acid, 15-hydroxypalmitic acid, and hydroxy-derivatives of other fatty acids from the phospholipids of the microsomal membrane. Evidence was also obtained indicating the formation of ketopalmitic acid. |
