ES46. 5K, a novel esterase from mouse hepatic microsomes (Watanabe K., et al., Biochem. Mol. Biol. Int., 31, 25-30 (1993)), catalyzed hydrolysis of phthalate esters. ES46. 5K and mouse hepatic microsomes hydrolyzed diethyl-, dibutyl-, diisobutyl-, dioctyl-and diethylhexyl phthalates, whereas dicyclohexyl-and diphenyl phthalates having ring structure were not hydrolyzed by the enzymes. V max (μmol/min/mg protein)/K m (μM) ratios of ES46. 5K for ...