title: A comparison of two novel alcohol dehydrogenase enzymes (ADH1 and ADH2) from the extreme halophile Haloferax volcanii.
abstract: Haloarchaeal alcohol dehydrogenases are exciting biocatalysts with potential industrial applications. In this study, two alcohol dehydrogenase enzymes from the extremely halophilic archaeon Haloferax volcanii (HvADH1 and HvADH2) were homologously expressed and subsequently purified by immobilized metal-affinity chromatography. The proteins appeared to copurify with endogenous alcohol dehydrogenases, and a double Δadh2 Δadh1 gene deletion strain was constructed to prevent this occurrence. Purified HvADH1 and HvADH2 were compared in terms of stability and enzymatic activity over a range of pH values, salt concentrations, and temperatures. Both enzymes were haloalkaliphilic and thermoactive for the oxidative reaction and catalyzed the reductive reaction at a slightly acidic pH. While the NAD(+)-dependent HvADH1 showed a preference for short-chain alcohols and was inherently unstable, HvADH2 exhibited dual cofactor specificity, accepted a broad range of substrates, and, with respect to HvADH1, was remarkably stable. Furthermore, HvADH2 exhibited tolerance to organic solvents. HvADH2 therefore displays much greater potential as an industrially useful biocatalyst than HvADH1.
authors.affiliation: Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Timpson
authors.forename: Ann-Kathrin
authors.initials: AK
authors.lastname: Liliensiek
authors.forename: Diya
authors.initials: D
authors.lastname: Alsafadi
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cassidy
authors.forename: Michael A
authors.initials: MA
authors.lastname: Sharkey
authors.forename: Susan
authors.initials: S
authors.lastname: Liddell
authors.forename: Thorsten
authors.initials: T
authors.lastname: Allers
authors.forename: Francesca
authors.initials: F
authors.lastname: Paradisi
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D003067:Coenzymes / Q000378:metabolism; D004795:Enzyme Stability; D015870:Gene Expression; D019622:Haloferax volcanii / Q000201:enzymology* / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012492:Salts / Q000378:metabolism; D012997:Solvents / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D003067:Coenzymes; D011994:Recombinant Proteins; D012492:Salts; D012997:Solvents; D000426:Alcohol Dehydrogenase