Production of 1, 2-Didocosahexaenoyl Phosphatidylcholine by Bonito Muscle Lysophosphatidylcholine/Transacylase

Abstract

1, 2-Didocosahexaenoyl phosphatidyleholine (PC), which has highly unsaturated fatty acid at both sn-1 and sn-2 positions of glycerol, is a characteristic molecular species of bonito muscle. To examine the involvement of a de novo route in its synthesis, the molecular species of phosphatidic acid (PA) were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using a 1, 3-bis [bis (pyridin-2-ylmethyl) amino] propan-2-olato dizine (II) complex, a novel phosphate-capture molecule. However, 1, 2-didocosahexaenoyl species could not be detected. Next, 1, 2-didocosahexaenoyl PC synthesis by the cytosolic lysophosphatidylcholine (LPC)/transacylase was examined using endogenous LPC from bonito muscle, in which the 2-docosahexaenoyl species is abundant. The LPC/transacylase synthesized 1, 2-didocosahexaenoyl PC as the most abundant molecular species. For further characterization, the LPC/transacylase was purified to homogeneity from the 100, 000×g supernatant of bonito muscle. The isolated LPC/transacylase is a labile glycoprotein with molecular mass of 52 kDa including a 5-kDa sugar moiety. The LPC/transacylase showed a PC synthesis (transacylase activity) below and above the critical micelle concentration of substrate LPC, and fatty acid release (lysophospholipase activity) was always smaller than the transacylase activity, even with a monomeric substrate. These results suggest that the LPC/transacylase is responsible for the synthesis of 1, 2-didocosahexaenoyl PC.