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A PHOSPHATIDYLINOSITOL SYNTHASE ACTIVITY FROM GERMINATNIG SOYBEAN SEEDS

1980; Wiley; Volume: 3; Issue: 2-3 Linguagem: Inglês

10.1111/j.1745-4514.1980.tb00638.x

1745-4514

George Carman, STEVEN M. FELDER,

Botanical Research and Chemistry

A membrane-associated CDP-1,2-diacyl-sn-glycerol (CDP-diacylglycerol): myo-insitol phosphatidyltransferase activity (phosphatidylinositol synthase, EC 2.7.8), was identified and partially characterized from a microsome preparation of germinating soybean seeds. The pH optimum for enzyme activity was pH 8.2 with Tris-HCl buffer. The dialyzed enzyme preparation had an absolute requirement for manganese (5 mM) or magnesium ions (50 mM). Increasing levels of Triton X-100 at molar ratios of 1:1 to 12:1 of Triton X-100 to CDP-diacylglycerol stimulated phosphatidylinositol synthase activity (about 10-fold) to a maximum followed by an inhibition of activity as the molar ratio was raised beyond the point of maximum activity. Phosphatidylserine, phosphatidylethanolamine, phosphatidylglycerol, sn-glycero-3-P, and choline inhibited activity while nucleotides stimulated activity. Phosphatidylinositol synthase activity was found to be thermally inactivated at temperatures above 40°C.