PROPERTIES OF PHOSPHOLIPASE A(1) TRANSACYLASE IN THE WHITE MUSCLE OF BONITO EUTHYNNUS-PELAMIS (LINNAEUS)

The properties of phospholipase A(1) (PLA(1)) obtained from the white muscle of bonito, Euthynrzus pelamis (Linnaeus), were examined. The PL A, activity had a pH optimum from 6.5 to 7.0 for phosphatidylcholine ( PC), and calcium ion was not required. The optimum temperature was fro m 20 to 30 degrees C. When a fatty alcohol was used as an acceptor, a wax ester was produced by transferring a fatty acid at the sn-1 positi on of the donor's PC. The maximum production of lysophosphatidylcholin e was shifted by 0.5 pH units to the acidic side and the pH optimum of wax ester synthesis was from 6.0 to 6.5. The synthesis was independen t of calcium ion and Coenzyme A. The transacylation was also observed when 1-lyso-2-acyl-sn-glycero-3-phosphocholine was used as an acceptor . Fatty acid at the sn-1 position of the donor PC was transferred to t he unoccupied hydroxy group of the acceptor at the sn-1 position. When 2,3-dipalmitoyl-sn-glycero-1-phosphocholine was used as the acyl dono r, a similar amount of palmitic acid was transferred as in the case of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. However, 1-acyl-2-lyso-s n-glycero-3-phosphocholine, a positional isomer, was a poor acceptor. These results indicate that the transacylation by the PLA(1) from boni to muscle is not stereospecific, but is position-specific both for the acyl donor and acceptor.