Haloacetonitriles Are Low KIInhibitors of Bacterial Dichloromethane Dehalogenases

Distinct dichloromethane dehalogenases from Methylobacteriumsp. strain DM4 and MethylophilusDM11 were inhibited by low concentrations of haloacetonitriles. Chloroacetonitrile (ClCH2CN) showed maximal inhibition at a stoichiometry of 1 mol inhibitor: 1 mol holoenzyme for both enzymes. This stoichiometry is suggestive of one active site per holoenzyme or extreme negative cooperativity amongst the subunits. Radiolahcllcd ClCH2CN dissociated completely or partially from the two dehalogenases, respectively, during chromatography. This suggested ClCH2CN was bound non-covalently.