SIMPLE TRANSPHOSPHATIDYLATION OF PHOSPHOLIPIDS CATALYZED BY A LIPID-COATED PHOSPHOLIPASE-D IN ORGANIC-SOLVENTS

A lipid-coated phospholipase D (PLD) was prepared by mixing aqueous so lutions of PLD and lipids. The lipid-coated PLD showed a high catalyti c activity for transphosphatidylation of egg yolk phosphatidylcholine (egg-PC) with alcohols in two-phase benzene-acetate buffer solution. S ince both substrates and enzymes are soluble in the organic phase, the reaction proceeded in the benzene phase and the aqueous phase is requ ired to remove the produced choline moiety from the organic phase. Whe n a native PLD was employed instead of the lipid-coated PLD, the react ion was very slow (similar to 1/300 that of the lipid-coated PLD) beca use the reaction occurs at the interface of the lipophilic substrates and water-soluble enzymes. The transphosphatidylation catalysed by a l ipid-coated PLD could be applied in a manner widely independent of the nature of the head groups of the coating lipids and the polarity of t he organic solvents, and could be applied also on a large-scale (yield 1-2 g) synthesis to introduce various alcohols, sugars, and nucleic a cids at the head groups of phospholipids. We have determined substrate selectivity and Michaelis-Menten kinetics for a lipid-coated PLD and compared the results with those for the native PLD.