Stabilisation of the NAD+-reducing soluble [NiFe]-hydrogenase from Ralstonia eutropha H16 through modification with methoxy-poly(ethylene) glycol

It has lately been demonstrated that the NAD+-reducing soluble hydrogenase from Ralstonia eutropha H16 (SH) is a promising catalyst for the regeneration of NADH in biocatalysed asymmetric redox reactions. Such reactions often require the presence of water-miscible organic solvents and ionic liquids to enable efficient application to organic synthesis. In this study, we investigated the influence of frequently used solubilisers such as dimethyl sulphoxide [DMSO] and Tris (2-hydroxyethyl) methylammonium methylsulphate [MTEOA][MeSO4] on the activity and stability of SH. The stability of the enzyme was significantly improved by covalent attachment of methoxy-poly(ethylene) glycol (mPEG). This modification led to significant increase of the half-life time from 0.1 to 0.5 h in the presence of 10% (v/v) isopropanol. Interestingly, no stabilisation was observed for ionic liquids, while the activity of SH increased by up to 45.5%. The mechanism(s) underlying these effects are discussed.