ACYLATION OF ENDOGENOUS ACYL ACCEPTORS BY MOUSE SCIATIC-NERVE MICROSOMES

Phospholipid (chiefly phosphatidylcholine) labeling from radioactive a cyl-CoAs by mouse sciatic nerve microsomes is observed in the absence of added acyl accepters. The maximal acylation (ca 10% of administered ) for 10 mu g microsomal proteins is observed at relatively low amount s of oleoyl-CoA (0.2-0.3 nmol) and decreases as the acyl-CoA amount in creases. Labeled lysophosphatidylcholine (almost exclusively esterifie d al position 2) is also observed, particularly when the [l-C-14]oleoy l-CoA concentration is higher than 0.2-0.3 nmol/50 mu l. The labeled a cyl group is mainly inserted in position 2 of the glycerophosphorylcho line. With 0.15 nmol labeled oleoyl-CoA, phosphatidylcholine acylation increases as a function of the protein amount and reaches 25% of the added label at 40 mu g proteins. It is evaluated that, in the presence of 10 mu g proteins, 2% of the microsomal phosphatidylcholine molecul es are acylated from 0.1 nmol acyl-CoA. The acylation mechanism seems to involve an acyl exchange between acyl-CoA and phosphatidylcholine.