Identification of the catalytic triad in the haloalkane dehalogenase from Sphingomonas paucimobilis UT26

The haloalkane dehalogenase from Sphingomonas paucimobilis UT26 (LinB) is t he enzyme involved in the gamma-hexachlorocyclohexane degradation. This enz yme hydrolyses a broad range of halogenated aliphatic compounds,ia an alkyl -enzyme intermediate. LinB is believed to belong to the family of alpha/bet a-hydrolases which employ a catalytic triad, i.e. nucleophile-histidine-aci d, during the catalytic reaction, The position of the catalytic triad withi n the sequence of LinB Nas probed by a site-directed mutagenesis. The catal ytic triad residues of the haloalkane dehalogenase LinB are proposed to be D108, H272 and E132. The topological location of the catalytic acid (E132) is after the beta-strand six which corresponds to the location of catalytic acid in the pancreatic lipase, but not in the haloalkane dehalogenase of X anthobacter autotrophicus GJ10 which contains the catalytic acid after the beta-strand seven. (C) 1999 Federation of European Biochemical Societies.