Separation of 1-Acylglycerolphosphate Ai 1-Acylglycerolphosphorylcholine Acyltrai

Acylglycerolphosphate acyltransferase (EC 2.3.1.-) and l-acylglycerolphlosphlorylcholine acyl- transferase (EC 2.3.1.23) of rat liver microsomes were sepa- rated from each other. The separation was achieved by sucrose density gradient centrifuigation of the enzyme preparation that was obtained by solubilizing microsomes with a nonionic detergent, Triton X-100, and subjecting the solubilized microsomes to molecular-sieve chroma- tography. The two acyltransferases are distinguishable from each other also with respect to their stabilities to heat and to Triton X-100. Hence, it is concluded that these acyltransferases are distinct enzymes. These results, to- gether with our previous finding that glycerolphosphate acyltransferase is also a separate enzyme, demonstrate the presence of distinct acyltransferases responsible for the acylation of the different acyl acceptors. Furthermore, the acyl-donor specificities of these acyltransferases pro- vide the enzymatic basis for the nonrandom distribution of fatty acids in naturally occurring glycerolipids.