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Plant Physiology 70:1664-1666 (1982) © 1982 American Society of Plant Biologists Biosynthesis of Indol-3-yl-acetyl-myo-inositol Arabinoside in Kernels of Zea mays L. 1Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824
Extracts of immature kernels of Zea mays L. catalyzed the synthesis of indol-3-yl-acetyl-myo-inositol arabinoside from indol-3-yl-acetyl-myo-inositol and UDP-[U-14C]xylose. The product contained radioactivity which upon hydrolysis with trifluoroacetic acid cochromatographed with arabinose and not xylose. The amount of product from the reaction was proportional to the amount of indol-3-yl-acetyl-myo-inositol added, and the product was positive to Ehmann's reagent for indoles. In addition, the product and authentic indol-3-yl-acetyl-myo-inositol arabinoside had the same RF or retention time in three chromatographic systems. By analogy to the wheat germ system, it is proposed that a UDP-D-xylose 4-epimerase is present in immature kernels of maize and that this enzyme catalyzes the conversion of UDP-D-xylose to UDP-L-arabinose, the probable sugar donor to indol-3-yl-acetyl-myo-inositol. The present data demonstrates the presence of a previously undescribed enzyme, UDP-arabinose:indol-3-yl-acetyl-myo-inositol arabinosyl transferase in maize kernels. This work together with our prior studies provides a pathway for the biosynthesis of all the low molecular weight esters of indol-3-yl-acetic acid in maize kernels.
2 Present address: Facultad de Ciencias Básicas y Farmacéuticas, Universidad de Chile, Casilla 653, Santiago, Chile. 1 Supported by a grant (PCM 79-04637) from the Metabolic Biology Section of the United States National Science Foundation and by the Life Sciences Program of the National Aeronautics and Space Administration (NASA-NAGW-97, ORD 25796). This is Journal Article 10473 from the Michigan Agricultural Experiment Station.
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