title: Purification and characterization of a novel recombinant highly enantioselective short-chain NAD(H)-dependent alcohol dehydrogenase from Thermus thermophilus.
abstract: The gene encoding a novel alcohol dehydrogenase (ADH) that belongs to the short-chain dehydrogenase/reductase (SDR) superfamily was identified in the extremely thermophilic, halotolerant gram-negative eubacterium Thermus thermophilus HB27. The T. thermophilus ADH gene (adh(Tt)) was heterologously overexpressed in Escherichia coli, and the protein (ADH(Tt)) was purified to homogeneity and characterized. ADH(Tt) is a tetrameric enzyme consisting of identical 26,961-Da subunits composed of 256 amino acids. The enzyme has remarkable thermophilicity and thermal stability, displaying activity at temperatures up to approximately 73 degrees C and a 30-min half-inactivation temperature of approximately 90 degrees C, as well as good tolerance to common organic solvents. ADH(Tt) has a strict requirement for NAD(H) as the coenzyme, a preference for reduction of aromatic ketones and alpha-keto esters, and poor activity on aromatic alcohols and aldehydes. This thermophilic enzyme catalyzes the following reactions with Prelog specificity: the reduction of acetophenone, 2,2,2-trifluoroacetophenone, alpha-tetralone, and alpha-methyl and alpha-ethyl benzoylformates to (S)-(-)-1-phenylethanol (>99% enantiomeric excess [ee]), (R)-alpha-(trifluoromethyl)benzyl alcohol (93% ee), (S)-alpha-tetralol (>99% ee), methyl (R)-(-)-mandelate (92% ee), and ethyl (R)-(-)-mandelate (95% ee), respectively, by way of an efficient in situ NADH-recycling system involving 2-propanol and a second thermophilic ADH. This study further supports the critical role of the D37 residue in discriminating NAD(H) from NADP(H) in members of the SDR superfamily.
authors.affiliation: Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131 Naples, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Pennacchio
authors.forename: Biagio
authors.initials: B
authors.lastname: Pucci
authors.forename: Francesco
authors.initials: F
authors.lastname: Secundo
authors.forename: Francesco
authors.initials: F
authors.lastname: La Cara
authors.forename: Mosè
authors.initials: M
authors.lastname: Rossi
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Raia
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D000595:Amino Acid Sequence; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D013237:Stereoisomerism; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D009243:NAD; D000426:Alcohol Dehydrogenase