Lipids in Cryptomonas CR-1. II. Biosynthesis of Betaine Lipids and Galactolipids

概要

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The biosynthesis of lipids in Cryptomonas strain CR-1 was studied using radioactive tracers. For studies of general aspects of the biosynthesis of lipids, the cells were labelled with [^<14>C]NaHCO_3 or with [1,3-^<14>14]glycerol. In both cases, monogalactosyl diacylglycerol (MGDG) was the most heavily labelled lipid. Phosphatidylcholine and the alanine lipid DGTA were not labelled to specific activities comparable to those of MGDG and DGDG. It is improbable that the so called "eukaryotic pathway", which has been suggested as the pathway for the synthesis of "eukaryotic" molecular species of MGDG from PC in higher plants, is operative in Cryptomonas cells which contain typical "eukaryotic" MGDG. The homoserine lipid DGTS was labelled to a significant level only in its polar group. The C-3 and C-4 atoms of methionine, as well as the methyl carbon of methionine, were incorporated into both DGTS and DGTA, whereas the C-1 carbon of methionine was incorporated uniquely into DGTS. Results of pulse-chase experiments with [3,4-^<14>C]methionine and [methyl-^<14>C]methionine suggest the conversion of DGTS to DGTA.
日本植物生理学会の論文