Biodegradation of alpha-hexachlorocyclohexane. VII. Resolution, purification, and characterization of an alpha-HCH dechlorinating enzyme from rat liver cytosol.

From rat liver cytosol, an enzyme was isolated which catalyzes the dechlorination of alpha-, gamma-, and delta-HCH. The enzyme also catalyzes the conjugation of GSH with 1,2-dichloro-4-nitrobenzene, and with 1 -chloro-2,4-dinitrobenzene. The enzyme has a molecular weight of about 46000 and its molecule is composed of two subunits of similar size. The optimum for the dechlorination of alpha-HCH lies at pH 8.0. The Michaelis constant is 0.12 mM for alpha-HCH (with 1 mM GSH as constant substrate), and maximal velocity was determined to be 0.25 moles Cl- -min -1 per mole enzyme.