Lipid Biosynthesis in the Blue-Green Alga (Cyanobacterium), Anabaena variabilis III. UDPglucose:Diacylglycerol Glucosyltransferase Activity in vitro

The synthesis of glyceroglycolipids was studied in membraneand soluble fractions of Anabaena variabilis. The membrane fractionexhibited a high activity of UDPglucose: diacylglycerol glucosyltransferase,but practically no activity of UDPgalactose: diacylglycerolgalactosyltransferase. The glucosyltransferase activity wasmaximal at about pH 7.0 and dependent on Mg²⁺ The Michaelisconstant (K_m) for UDPglucose was 45?10^–6 M. The solublefraction catalyzed the incorporation of galactose from UDP galactoseinto digalactosyl diacylglycerol. These in vitro results werecompatible with the biosynthetic pathway of glyceroglycolipidsin this alga that we previously elucidated on the basis of tracerexperiments in vivo. ¹ Present address: Department of Biology, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan. (Received June 1, 1982; Accepted July 1, 1982)