Comparison of the acylation of sn-glycerol 3-phosphate and membrane-bound lipid in the microsomal fraction from rabbit brain throughout maturation.

1. Age-related changes in the specific activity of palmitoyl-CoA synthetase, sn-glycerol 3-phosphate acyltransferase (EC 2.3.1.15) and the esterification of [3H]palmitate into endogenous lipid in the microsomal fraction from rabbit brain have been determined throughout development. 2. The increased specific activity of sn-glycerol 3-phosphate acyltransferase at the onset of myelination (rising in parallel with other lipogenic enzymes) is consistent with a direct role of the acyltransferase in promoting the accumulation of cerebral lipid. In adult brain microsomes, although the specific activity was low, the total activity was only 20% lower than during active myelination. 3. Palmitoyl-CoA, synthesized by the palmitoyl-CoA synthetase in the microsomal membrane, was the preferred substrate for the esterification of sn-glycerol 3-phosphate. There was no evidence for a pool of palmitoyl-CoA formed from palmitate. 4. The esterification of [3H]palmitate into membrane-bound lipid remained high throughout development and may be part of an acyl-exchange cycle via lysophospholipids. [3H]palmitate was incorporated into both neutral lipids and phospholipids, while phosphatidic acid was the major product of sn-[1(3)-3H]-glycerol-3-phosphate esterification. 5. The microsomal fraction contained a pool of unesterified fatty acid, which was activated and esterified into sn-glycerol 3-phosphate.