ENZYMIC-SYNTHESIS OF "1-0-INDOL-3-YLACETYL-BETA-D-GLUCOSE AND INDOL-3-YLACETYL-MYO-INOSITOL

An enzyme fraction from extracts of immature kernels of Z. mays catalyzes the formation of 1-O-indol-3-ylacetyl-.beta.-D-glucose from indol-3-ylacetic acid and UDP-glucose. A 2nd enzyme fraction catalyzes the formation of indol-3-ylacetyl-myo-inositol from 1-O-indol-3-ylacetyl-.BETA.-D-glucose and myo-inositol. This is the 1st example of hydroxy-group acylation by a 1-O-acyl sugar. A reaction sequence is proposed. The enzyme catalyzing reaction (1) is UDP-glucose:indol-3-ylacetate glucosyltransferase (indol-3-ylacetylglucose synthase), and that catalyzing reaction (2) is indol-3-ylacetylglucose:myo-inositol indol-3-ylacetyltransferase (indol-3-ylacetyl-myo-inositol synthase). Indol-3-ylacetylglucose synthase is specific for UDP-glucose and, at the stage of purity tested, the enzyme will use either IAA or naphthalene-1-acetic acid, but not 2,4-D acid, as glucose acceptor. The indol-3-ylacetyl-myo-inositol synthase is specific for indol-3-ylacetylglucose and will not use naphthalene-1-acetylglucose as substrate, and it is specific for myo-inositol among the alcohol acceptors tested. Of the auxins tested, only IAA forms the myo-inositol ester.