Positional Distribution of Fatty Acids in Glycerolipids of the Marine Red Alga, Porphyra yezoensis

The positional distribution of fatty acids in glycerolipids from thalli of Porphyra yezoensis was studied by enzymatic hydrolysis. In monogalactosyl diacylglycerol, icosapentaenoic acid was a major fatty acid at both the sn-1 and sn-2 positions of the glycerol moiety, whereas palmitic acid was a minor component at both positions. In digalactosyl diacylglycerol and sulfoquinovosyl diacylglycerol, icosapentaenoic and palmitic acids were almost exclusively distributed at the sn-1 and sn-2 positions, respectively. In phosphatidylglycerol, palmitic and trans-ω-13-hexadecenoic acid were exclusively located at the sn-2 position. In phosphatidylcholine, icosapentaenoic acid occurred in both the sn-l and sn-2 positions, whereas palmitic acid was confined to the sn-1 position. It is suggested that monogalactosyl diacylglycerol in P. yezoensis synthesized in both the cytoplasmic and chloroplastic pathways, while the diacylglycerol moieties of the other chloroplast lipids are virtually all derived from the chloroplastic pathway.