title: Stability and sulfur-reduction activity in non-aqueous phase liquids of the hydrogenase from the hyperthermophile Pyrococcus furiosus.
abstract: Hydrogenase from the hyperthermophilic archaeon, Pyrococcus furiosus, catalyzes the reversible activation of H(2) gas and the reduction of elemental sulfur (S degrees ) at 90 degrees C and above. The pure enzyme, modified with polyethylene glycol (PEG), was soluble (> 5 mg/mL) in toluene and benzene with t(1/2) values of more than 6 h at 25 degrees C. At 100 degrees C the PEG-modified enzyme was less stable in aqueous solution (t(1/2) approximately 10 min) than the native (unmodified) enzyme (t(1/2) approximately 1 h), but they exhibited comparable H(2) evolution, H(2) oxidation, and S degrees reduction activities at 80 degrees C. The H(2) evolution activity of the modified enzyme was twice that of the unmodified enzyme at 25 degrees C. The PEG-modified enzyme did not catalyze S degrees reduction (at 80 degrees C) in pure toluene unless H(2)O was added. The mechanism by which hydrogenase produces H(2)S appears to involve H(2)O as the proton source and H(2) as the electron source. The inability of the modified hydrogenase to catalyze S degrees reduction in a homogeneous non-aqueous phase complicates potential applications of this enzyme.
authors.affiliation: Department of Biochemistry and Molecular Biology, Life Sciences Building, University of Georgia, Athens, Georgia 30602-7229, USA.
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.forename: C A
authors.initials: CA
authors.lastname: Woodward
authors.forename: E N
authors.initials: EN
authors.lastname: Kaufman
authors.forename: M W
authors.initials: MW
authors.lastname: Adams
mesh_terms: D001709:Biotechnology; D004795:Enzyme Stability; D006358:Hot Temperature; D006859:Hydrogen / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism; D006864:Hydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D011092:Polyethylene Glycols; D020027:Pyrococcus furiosus / Q000201:enzymology*; D012995:Solubility; D012997:Solvents; D013455:Sulfur / Q000378:metabolism
chemical_list: D012997:Solvents; D011092:Polyethylene Glycols; D013455:Sulfur; D006859:Hydrogen; D006864:Hydrogenase; D006862:Hydrogen Sulfide