ISOLATION, CHEMICAL CHARACTERIZATION, AND SUBCELLULAR-DISTRIBUTION OF1-O-ALKYL-2-ACETYL-SN-GLYCEROL IN TETRAHYMENA-PYRIFORMIS CELLS

1-O-Hexadecyl-2-acetyl-sn-glycerol, the immediate precursor of platele t-activating factor (PAF) in its de nova formation, was detected in th e protozoon Tetrahymena pyriformis. It was purified from the total lip id extract by TLC, after successive developments in two different solv ent systems. Characterization was assessed by (a) gas-liquid chromatog raphy with electron capture detection, and (b) gas chromatography comb ined with mass spectrometry in selected ion monitoring mode, after der ivatization with heptafluorob utyric acid anhydride and tert-butyldime thylchlorosilane/imidazole respectively. Its quantity was found to be 0.1 nmol/10(7) cells from the CC-MS, using authentic alkylacetylglycer ol as external standard, Cell fractionation revealed that alkylacetylg lycerol is located exclusively in the microsomal fraction of the proto zoon. Previously, we have reported the occurrence of PAF in the micros omal fraction, as well as a dithiothreitol-insensitive CDP-choline: ch olinephosphotransferase activity that utilizes exogenous alkylacetylgl ycerol as substrate in the mitochondrial and microsomal fractions. The above findings indicate that PAF can be formed in the cell by the de novo pathway.