title: Purification and characterization of thermostable and nonthermostable 2-haloacid dehalogenases with different stereospecificities from Pseudomonas sp. strain YL.
abstract: Two novel hydrolytic dehalogenases, thermostable L-2-haloacid dehalogenase (L-DEX) inducibly synthesized by 2-chloropropionate (2-CPA) and nonthermostable DL-2-haloacid dehalogenase (DL-DEX) induced by 2-chloroacrylate, were purified to homogeneity from Pseudomonas sp. strain YL. DL-DEX consisted of a monomer with a molecular weight of about 36,000 and catalyzed the dehalogenation of L and D isomers of 2-CPA to produce D- and L-lactates, respectively. It acted on 2-haloalkanoic acids with a carbon chain length of 2 to 4. The maximum activity on DL-2-CPA was found at pH 10.5 and 45 degrees C. L-DEX, composed of two subunits with identical molecular weights of 27,000, catalyzes the dehalogenation of L-2-haloalkanoic acids to produce the corresponding D-2-hydroxyalkanoic acids. The enzyme acts not only on short-carbon-chain 2-haloacids such as monochloroacetate and monoiodoacetate in aqueous solution but also on long-carbon-chain 2-haloacids such as 2-bromohexadecanoate in n-heptane. L-DEX is thermostable: it retained its full activity upon heating at 60 degrees C for 30 min. The pH and temperature optima for dehalogenation of L-2-CPA were 9.5 and 65 degrees C, respectively. L-DEX was strongly inhibited by modification of carboxyl groups with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and Woodward reagent K, but DL-DEX was not.
authors.affiliation: Laboratory of Microbial Biochemistry, Institute for Chemical Research, Kyoto University, Japan.
authors.forename: J Q
authors.initials: JQ
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Kurihara
authors.forename: A K
authors.initials: AK
authors.lastname: Hasan
authors.forename: V
authors.initials: V
authors.lastname: Nardi-Dei
authors.forename: H
authors.initials: H
authors.lastname: Koshikawa
authors.forename: N
authors.initials: N
authors.lastname: Esaki
authors.forename: K
authors.initials: K
authors.lastname: Soda
mesh_terms: D000595:Amino Acid Sequence; D004795:Enzyme Stability; D006536:Heptanes; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011487:Protein Conformation; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D006536:Heptanes; C028618:n-heptane; D006867:Hydrolases; C034507:2-haloacid dehalogenase