Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts

Soluble acyl-CoA:sn-glycerol 3-phosphate acyltransferases (EC 2.3.1.15) which are localized in chloroplasts were purified from leaves of Pisum sativum and Spinacia oleracea and obtained free from interfering activities. The purification raised the specific activities by factors of about 1,000 for pea and 200 for spinach preparations. In pea chloroplasts, acyltransferase activity occurs in two soluble forms with apparent isoelectric points of 6.3 and 6.6. For both forms, the same molecular weight of about 42,000 was determined. The enzyme from spinach chloroplasts showed a slightly higher molecular weight and a lower isoelectric point of 5.2.