Uridine diphosphate glucose:fatty acid glucosyl transferase activity of rape (Brassica napus L.) anther tissue

Particulate fractions from mature rape anther tissue catalysed the incorporation of glucose from UDPglucose into endogenous lipids. The UDPglucose:fatty acid glucosyl transferase was tightly bound to particulates that could be suspended in 0.1% Triton X-100. The apparent Km for UDPglucose was 3.5 . 10(-6) M. In Tris buffer the enzyme has a pH optimum of 8.0 and a temperature optimum of 30 degrees C. In the presence of NaF, the transferase activity was proportional to protein concentration, time, and other variables of the reaction mixture. ADPglucose, GDPglucose, and CDPglucose did not compete with the activity of the UDP-glucose-dependent glucosyl transferase. Gas chromatographic and high performance liquid chromatographic analyses indicated that the endogenous fatty acids glucosylated in vitro had carbon chain lengths of C16 to C20. This is the first report on the biosynthesis of non-phosphorylated glucosyl esters of fatty acids in higher plants.