Stability and sulfur-reduction activity in non-aqueous phase liquids of the hydrogenase from the hyperthermophile Pyrococcus furiosus
✍ Scribed by Chulhwan Kim; Charlene A. Woodward; Eric N. Kaufman; Michael W. W. Adams
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 110 KB
- Volume
- 65
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
Hydrogenase from the hyperthermophilic archaeon, Pyrococcus furiosus, catalyzes the reversible activation of H 2 gas and the reduction of elemental sulfur (S°) at 90°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°C. At 100°C the PEG-modified enzyme was less stable in aqueous solution (t 1/2 ∼ 10 min) than the native (unmodified) enzyme (t 1/2 ∼ 1 h), but they exhibited comparable H 2 evolution, H 2 oxidation, and S°reduction activities at 80°C. The H 2 evolution activity of the modified enzyme was twice that of the unmodified enzyme at 25°C. The PEG-modified enzyme did not catalyze S°reduction (at 80°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°reduction in a homogeneous nonaqueous phase complicates potential applications of this enzyme.