Metabolism of the Phosphatidylglycerol Molecular Species in Escherichia coli

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Abstract
The fractionation, turnover and biosynthesis of the phosphatidylglycerol molecular species of Escherichia coli were studied. Monoacetyldiglycerides derived from phosphatidylglycerol were separated into five subfractions; cis-vaccenyl-palmitoleyl, cis-vaccenyl-cis-vaccenyl, palmityl-palmitoleyl, palmityl-cis-vaccenyl and the disaturated molecular species on a silica gel plate impregnated with silver nitrate. Individual molecular species had different turnover rates. The palmityl-cis-vaccenyl species was metabolized faster than the others. Disaturated species were rather stable. Various phosphatidylglycerol molecular species were synthesized in the presence of sn-glycerol 3-phosphate, palmityl-CoA, palmitoleyl-CoA, cis-vaccenyl-CoA and CTP by the E. coli membrane particulate fraction. When only the proportion of palmityl-CoA among the three acyl-CoAs was increased, the molecular species containing the palmityl residue were increased. Similar results were obtained with the other acyl-CoAs. However, a temperature-sensitive incorporation of unsaturated and saturated fatty acids into phosphatidylglycerol molecular species was observed with no change in the proportions of the three acyl-CoAs, completely reflecting the in vivo unsaturated/saturated ratio.

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