Phosphatidyldiglucosyl diglyceride from Streptococci and its relationship to other polar lipids

Abstract

1. 1. The less polar phosphoglucolipid from Streptococcus faecalis was isolated. It contained D-glucose, glycerol, fatty acid ester and phosphorus in a molar ratio of approx. 2:2:4:1. 2. 2. The structure was shown to be 3(1)- O-[6'-(1,2-diacyl- sn-glycero-3-phosphoryl) -2'-O-(α- D-glucopyranosyl)-α- D-glucopyranosyl]-1(3),2-diacylglycerol. 3. 3. Structural analysis of the deacylated core was based on periodate oxidation, Smith degradation, alkaline hydrolysis and enzymatic degradation. The location of the acyl groups was achieved by degradation of the phosphoglucolipid with 60% HF (w/v) resulting in the formation of diglycerides and diglucosyl diglyceride. 4. 4. Isolation of these breakdown products, cleavage of the diglucosyl diglyceride with a position-specific lipase and treatment of the intact lipid with phospholipase A 2 were used to analyze the fatty acid distribution. 5. 5. The fatty acid composition of the phosphoglucolipid and its two diglyceride portions was identical. Each of the latter showed a non-random distribution with long-chain fatty acids dominating Position 1 and shorter-chain fatty acids dominating Position 2. 6. 6. Diglucosyl diglyceride, diphosphatidylglycerol and phosphatidylglycerol of S. faecalis showed the same fatty acid composition and distribution pattern as the phosphoglucolipid, suggesting close biosynthetic relationships. 7. 7. Reinvestigation of the phosphoglucolipid from Streptococcus lactis (Fischer W. (1970) Biochem. Biophys. Res. Commun. 41, 731–736) established four acyl groups with the same location as in the phosphoglucolipid of S. faecalis.