Possesses low catalytic activity in vitro. Also active as glucosyltransferase in vitro on benzoates and benzoate derivatives. (indol-3-yl)acetate + UDP-alpha-D-glucose = 1-O-(indol-3-ylacetyl)-beta-D-glucose + UDP Plant hormone metabolism; auxin conjugation. Belongs to the UDP-glycosyltransferase family.