Partial purification and characterization of indol-3-ylacetylglucose:myo-inositol indol-3-ylacetyltransferase (indoleacetic acid-inositol synthase).
A procedure is described for the purification of the enzyme indol-3-ylacetylglucose:myo-inositol indol-3-ylacetyltransferase (IAA-myo-inositol synthase).  This enzyme catalyzes the transfer of indol-3-ylacetate from 1-0-indol-3-ylacetyl-beta-d-glucose to myo-inositol to form indol-3-ylacetyl-myo-inositol and glucose.  A hexokinase or glucose oxidase based assay system is described.  The enzyme has been purified approximately 16,000-fold, has an isoelectric point of pH 6.1 and yields three catalytically inactive bands upon acrylamide gel electrophoresis of the native protein.  The enzyme shows maximum transferase activity with myo-inositol but shows some transferase activity with scyllo-inositol and myo-inosose-2.  No transfer of IAA occurs with myo-inositol-d-galactopyranose, cyclohexanol, mannitol, or glycerol as acyl acceptor.  The affinity of the enzyme for 1-0-indol-3-ylacetyl-beta-d-glucose is, Km =  30 micromolar, and for myo-inositol is, Km = 4 millimolar.  The enzyme does not catalyze the exchange incorporation of glucose into IAA-glucose indicating the reaction mechanism involves binding of IAA glucose to the enzyme with subsequent hydrolytic cleavage of the acyl moiety by the hydroxyl of myo-inositol to form IAA myo-inositol ester.
Kesy
J M
JM
Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824-1312, USA.
Bandurski
R S
RS
D000217:Acyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D004952:Esters / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism*; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology* / Q000378:metabolism
D004952:Esters; D007210:Indoleacetic Acids; D007294:Inositol; D000217:Acyltransferases; C025402:indoleacetyl-glucose-myo-inositol indoleacetyl transferase; D005947:Glucose