Cytidine Diphosphate Diglyceride of Bovine Brain. Positional Distribution of Fatty Acids and Analysis of Major Molecular Species

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Abstract
A method was described for the isolation of CDP-diglyceride from bovine brain. Yields of the product ranged from 9.2-15.5 .mu.mol/kg of tissue, which corresponded to about 1% of the level of phosphatidic acid. Mild Alkaline hydrolysis of the product gave 3 water-soluble phosphate esters which had the same electrophoretic mobilities as CMP, CDP-glycerol and glycerol 3-phosphate. The liponucleotide was quantitatively hydrolyzed by CDP-diglyceride hydrolase from Escherichia coli to phosphatidic acid and CMP. No dCMP was recovered in enzymatic or alkaline hydrolysates, and there is apparently little or no dCDP-diglyceride in bovine brain. Brain CDP-diglyceride was similar to phosphatidylinositol in that in both lipids stearate was the major saturated fatty acid and arachidonate the most abundant unsaturated fatty acid. This differed significantly from the fatty acid patterns of other metabolically related phospholipids, phosphatidic acid and cardiolipin. Brain CDP-diglyceride was hydrolyzed with phospholipase C from Clostridium welchii with the liberation of the diglyceride moiety in high yield. Treatment of the diglyceride with pancreatic lipase showed CDP-diglyceride with the asymmetric distribution of fatty acids characteristic of most mammalian phospholipids, saturated fatty acids being found mostly at position 1 and polyunsaturated fatty acids at position 2. The derived diglyceride acetates were separated into different molecular species by argentation TLC. These analyses showed that 1-stearoyl, 2-arachidonoyl was the major species of brain CDP-diglyceride.