Possesses quercetin 3-O-glucosyltransferase and low 7-O-glucosyltransferase activities in vitro. Also active in vitro on benzoates and benzoate derivatives. Can detoxify the explosive 2,4,6-trinitrotoluene in plant by forming O- or C-glucose conjugates. a flavonol + UDP-alpha-D-glucose = a flavonol 3-O-beta-D-glucoside + H(+) + UDP Specifically expressed in roots. Induced by pathogen infection and salicylic acid. Plants overexpressing UGT73B4 show enhanced root growth in seedlings grown in presence of 2,4,6-trinitrotoluene. Belongs to the UDP-glycosyltransferase family. Truncated N-terminus.