Pedro M. Matias, Marta C. Marques, Ricardo Coelho and Inês A. C. Pereira
ITQB, Universidade Nova de Lisboa, Av. República, EAN, 2780 Oeiras Portugal
At a critical stage of the fossil fuel crisis and global warming, hydrogen is drawing increased attention as an energy carrier with great potential to become an environment-friendly fuel in the future. Using hydrogenases, biological hydrogen production from renewable sources can replace the expensive Pt-based catalysts presently used to transform fossil fuels. Hydrogenases can also be used in bioelectrical devices for the direct conversion of hydrogen into electricity.
The most studied hydrogenases are of the [NiFe] type, and while most [NiFe] hydrogenases are inactivated by oxygen, the few known O2-tolerant enzymes are hydrogen-uptake enzymes, unsuitable for hydrogen production, due to strong product inhibition. In contrast, the [NiFeSe] hydrogenases, where a selenocysteine is bound to the nickel, are very attractive alternatives because of their high hydrogen production activity and fast reactivation after O2 exposure.
High-resolution crystallographic 3D structures of the soluble form of the [NiFeSe] hydrogenase from D. vulgaris Hildenborough in three different redox states (oxidized as-isolated, H2-reduced and air re-oxidized) have revealed the structural changes that take place at the active site during enzyme reduction and re-oxidation. These results provide new insights into the pathways of O2 inactivation in [NiFeSe] hydrogenases, different from those found in [NiFe] hydrogenases. This knowledge is essential to understand their properties and for the correct design of devices using the [NiFeSe] enzymes for H2 production.
This work is based on experiments performed at the Swiss Light Source (SLS), Paul Scherrer Institute, Villigen, Switzerland and at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.°226716, and it was also supported by research grants PTDC/BIA-PRO/70429/2006 and PEst OE/EQB/LA0004/2011 funded by Fundação para a Ciência e Tecnologia (Portugal). The authors thank the ESRF for support and João Carita (ITQB) for growing the bacterial cells.
Marta C. Marques, Ricardo Coelho, Inês A. C. Pereira, Pedro M. Matias, "Redox State-Dependent Changes in the Crystal Structure of [NiFeSe] Hydrogenase from Desulfovibrio vulgaris Hildenborough" (2013) Int. J. Hydrogen Energ. doi: 10.1016/j.ijhydene.2013.04.132