Isomerization of 1-O-indol-3-ylacetyl-beta-D-glucose.  Enzymatic hydrolysis of 1-O, 4-O, and 6-O-indol-3-ylacetyl-beta-D-glucose and the enzymatic synthesis of indole-3-acetyl glycerol by a hormone metabolizing complex.
The first compound in the series of reactions leading to the ester conjugates of indole-3-acetic acid (IAA) in kernels of Zea mays sweet corn is the acyl alkyl acetal, 1-O-indol-3-ylacetyl-beta-D-glucose (1-O-IAGlu).  The enzyme catalyzing the synthesis of this compound is UDP-glucose:indol-3-ylacetate glucosyl-transferase (IAGlu synthase).  The IAA moiety of the high energy compound 1-O-IAGlu may be enzymatically transferred to myo-inositol or to  glycerol or the 1-O-IAGlu may be enzymatically hydrolyzed.  Alternatively, nonenzymatic acyl migration may occur to yield the 2-O, 4-O, and 6-O esters of IAA and glucose.  The 4-O and 6-O esters may then be enzymatically hydrolyzed to yield free IAA and glucose.  This work reports new enzymatic activities, the transfer of IAA from 1-O-IAGlu to glycerol, and the enzyme-catalyzed hydrolysis of 4-O and 6-O-IAGlu.  Data is also presented on the rate of non-enzymatic acyl migration of IAA from the 1-O to the 4-O and 6-O positions of glucose.  We also report that enzymes catalyzing the synthesis of 1-O-IAGlu and the hydrolysis of 1-O, 4-O, and 6-O-IAGlu fractionate as a hormone metabolizing complex.  The association of synthetic and hydrolytic capabilities in enzymes which cofractionate may have physiological significance.
Kowalczyk
S
S
Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824-1312.
Bandurski
R S
RS
D004951:Esterification; D005947:Glucose / Q000378:metabolism; D006867:Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D007210:Indoleacetic Acids / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors; D003313:Zea mays / Q000201:enzymology* / Q000378:metabolism*
D007210:Indoleacetic Acids; C030737:indoleacetic acid; D006867:Hydrolases; D005947:Glucose