Evidence that DDT-dehydrochlorinase from the house fly is a glutathione S-transferase

DDT-dehydrochlorinase has been isolated in a highly purified form by a procedure involving affinity chromatography, gel-permeation chromatography, and preparative isoelectrofocusing. At least two protein species appeared to possess DDT-dehydrochlorinase activity; the principal one of these was purified by a factor of 660-fold. This appeared to be dimeric with subunits of molecular weight of 23,000 and 25,000. Another protein with this activity appeared to consist of two identical subunits of M_r 25,000. The protein with greatest activity was isoelectric at pH 7.1. It was found to be homogeneous on analytical gel electrophoresis in both the presence and absence of SDS. The same protein generated a number of minor protein bands on analytical electrofocusing in polyacrylamide gels, but there is evidence that these bands may be artifactual. Both purified forms of the enzyme possessed substantial glutathione S-transferase activity with both CDNB and DCNB. An acidic protein, a dimer of subunits of M_r 23,000 had substantial GSH transferase activity with CDNB as substrate, but had no DDT-dehydrochlorinase activity.