Acylation of dog heart lysophosphatidylserine by transacylase activity

Dog heart microsomes catalyze the transfer of acyl groups from the sn-2 position of phosphatidylcholine (PC) to lysophosphatidylserine (lysoPS) in the presence of coenzyme A (CoA) at pH optima of 4.5-5.0 and 7.5. Acyl transfer activity at acidic pH is about three times higher than at neutral pH. Transacylation of lysoPS by acyl transfer from PC with dog heart microsomes at neutral pH favors arachidonate over linoleate by a factor of 2.1, whereas free linoleic acid is favored by a factor of 3.7 over arachidonic acid for lysoPS acylation in the presence of acyl-CoA-generating cofactors. Considering the location and acyl composition of myocardial PS, it appears that both acyl transfer from PC and utilization of unesterified fatty acids may be involved in the acylation of lysoPS at its sn-2 position.