Enzymic synthesis of 1-O-indol-3-ylacetyl-beta-D-glucose and indol-3-ylacetyl-myo-inositol.
An enzyme fraction from extracts of immature kernels of Zea mays catalyses the formation of 1-O-indol-3-ylacetyl-beta-D-glucose from indol-3-ylacetic acid and UDP-glucose. A second enzyme fraction catalyses the formation of indol-3-ylacetyl-myo-inositol from 1-O-indol-3-ylacetyl-beta-D-glucose and myo-inositol. To our knowledge, this is the first example of hydroxy-group acylation by a 1-O-acyl sugar. The following reaction sequence is proposed: Indol-3-ylacetic acid + UDP-glucose leads to indol-3-ylacetylglucose + UDP (1) Indol-3-ylacetylglucose + myo-inositol leads to indol-3-ylacetyl-myo-inositol + glucose (2) The enzyme catalysing reaction (1) is called UDP-glucose:indol-3-ylacetate glucosyl-transferase (indol-3-ylacetylglucose synthase), and that catalysing reaction (2) is indol-3-ylacetylglucose:myo-inositol indol-3-ylacetyltransferase (indol-3-ylacetyl-myo-inositol synthase). We further show that indol-3-ylacetylglucose synthase is specific for UDP-glucose and, at the stage of purity tested, the enzyme will use either indol-3-ylacetic acid or naphthalene-1-acetic acid, but not 2.4-dichlorophenoxyacetic acid, as glucose acceptor. The indol-3-ylacetyl-myo-inositol synthase is specific for indol-3-ylacetyl-glucose and will not use naphthalene-1-acetylglucose as substrate, and it is specific for myo-inositol among the alcohol acceptors tested. Thus, of the auxins tested, only indol-3-ylacetic acid forms the myo-inositol ester.
D000217:Acyltransferases / Q000378:metabolism; D005964:Glucosyltransferases / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D013379:Substrate Specificity; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D014544:Uridine Triphosphate / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology
D007210:Indoleacetic Acids; C037009:1-O-indol-3-ylacetylglucose; C037008:indol-3-ylacetylinositol; D000217:Acyltransferases; C025402:indoleacetyl-glucose-myo-inositol indoleacetyl transferase; D005964:Glucosyltransferases; C071643:indole-3-acetate beta-glucosyltransferase; D008274:Magnesium; D014544:Uridine Triphosphate; D014532:Uridine Diphosphate Glucose