Cytosolic lysophosphatidylcholine/transacylase in the production of dipolyunsaturated phosphatidylcholine in bonito muscle.

Phosphatidylcholine with docosahexaenoic acid at both sn-1 and sn-2 positions occurs in relatively high abundance in bonito muscle. To explore a possible route for the dipolyunsaturated molecular species, phosphatidylcholine formation from 2-[1-14C]linoleoyl lysophosphatidylcholine was examined using a cytosolic fraction from bonito muscle. The formation of radiolabeled phosphatidylcholine was greatest at 15 degrees C and did not require the presence of cofactors such as CoA and calcium. By DEAE-cellulofine column chromatography, the activity to form phosphatidylcholine was separated from that of phospholipase A1, and the specific activity increased by about 100-fold. The possible involvement of cytosolic lysophosphatidylcholine/transacylase in synthesis of dipolyunsaturated phosphatidylcholine is discussed.