title: Reconsideration of the essential role of a histidine residue of L-2-halo acid dehalogenase.
abstract: His20 of L-2-halo acid dehalogenase from Pseudomonas cepacia MBA4 was suggested to serve as a catalytic base [Biochem. J. (1993) 292, 69-74]. In this study, we substituted Asn or Leu for His19 of L-2-halo acid dehalogenase from Pseudomonas sp. YL, which corresponds to His20 of the P. cepacia enzyme. Although the substrate specificity was affected by the substitution, the susceptibilities of substrate halo acids were not substantially diminished, and the Km and kcat values of the mutant enzymes for L-2-chloropropionate were not significantly different from those of the wild-type enzyme. In addition, the wild-type and mutant enzymes showed the same pH optimum. Accordingly, His19 is not essential for catalysis of L-2-halo acid dehalogenase.
authors: Laboratory of Microbial Biochemistry, Kyoto University.
authors: J Q
authors: JQ
authors: Liu
authors: T
authors: T
authors: Kurihara
authors: N
authors: N
authors: Esaki
authors: K
authors: K
authors: Soda
mesh_terms: D001224:Aspartic Acid; D001426:Bacterial Proteins / Q000187:drug effects / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D006639:Histidine / Q000737:chemistry / Q000378:metabolism*; D006867:Hydrolases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D011549:Pseudomonas / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D001224:Aspartic Acid; D006639:Histidine; D006867:Hydrolases; C034507:2-haloacid dehalogenase