Anaerobic reactions of phospholipins in brain suspensions

Abstract

Lipid samples rich in phosphatidylserine were incubated under N with suspensions of guinea pig brain in media of pH 5-9. There was no conclusive evidence of decarboxylation of the phosphatidylserine to phosphatidylethanolamine; if such a reaction did occur, its max. rate was 2.4/imoles/g. wet wt./hr. Brain lipid samples of varied composition were incubated under 95% N + 5% CO2 (v/v) with suspensions of guinea pig brain in bicarbonate-saline at a pH of about 7.4. The evolution of CO2, in excess of that from the brain homogenates alone, suggested that some of these lipids were being hydrolyzed with the formation of free acid; the "inositol phosphatide" fraction of cephalin (containing about 40% of diphosphoinositide) reacted about 10 times as rapidly (avg. rate, corrected for blanks, 66[mu]moles/g. wet wt./hr.) as any of the other lipid samples. The evolution of CO2 from mixtures of brain suspensions with "inositol phosphatide" was accompanied by the release of about 2 molecular proportions of phosphate (about half organic) and one of combined inositol. Smaller amts. of N and of free inositol and glycerol were also found; but the main reaction appeared to have been the partial hydrolysis of diphosphoinositide.