The effect of membrane lipid molecular species on rat brain base-exchange reactions: an appraisal of phosphatidylserine and of polyunsaturated phosphatidylcholine.

Rat brain microsomal membranes were solubilized with octyl glucoside and reassembled by removing the detergent. The composition of reconstituted membranes was modified by adding exogenous lipid to the detergent-membrane mixtures. The base-exchange reactions were sensitive to these procedures. The inhibiting or activating capacity of added lipid was related to the charge of polar head groups; indeed, the addition of phosphatidylserine always resulted in inhibition and that of phosphatidylcholine very often in activation. The addition of phospholipid possessing unsaturated acyl chains inhibited less (or activated more) serine and choline base-exchange than the addition of saturated species. It is concluded that phosphatidylserine and polyunsaturated phosphatidylcholine have opposite effects on base-exchange.