Sn-Glycerol-3-phosphate acyltransferase in a particulate fraction from maturing safflower seeds

Abstract

The properties of the acyl-CoA: sn-glycerol-3-phosphate O-acyltransferase in a 20,0000 g particulate fraction from maturing safflower seeds were investigated. The optimum pH of the reaction was 7.2. The apparent K m for glycerophosphate was 0.54 m m. Only monoacylglycerophosphate was accumulated in the particulate fraction under normal conditions. Position 1 of glycerophosphate was exclusively esterified with either palmitoyl-CoA or linoleoyl-CoA as acyl donor, while 2-acylglycerophosphate was the minor product. The specificity and selectivity of the acyltransferase for acyl-CoA were broad and somewhat affected by temperature. The concentration of glycerophosphate did not affect the selectivity. These observations suggested that the fatty acid composition of position 1 of safflower triacylglycerol must primarily depend on the composition of the acyl-CoA pool in the site of synthesis, and that growth temperature and the acyl-CoA selectivity of the glycerophosphate acyltransferase may be rather minor factors regarding regulation of the fatty acid composition of position 1 in triacylglycerol.