The enterobacterium Escherichia coli synthesizes two H uptake enzymes, Hyd-1 and Hyd-2. We show using precise electrochemical kinetic measurements that the properties of Hyd-1 and Hyd-2 contrast strikingly, and may be individually optimized to function under distinct environmental conditions. Hyd-2 is well suited for fast and efficient catalysis in more reducing environments, to the extent that in vitro it behaves as a bidirectional hydrogenase. In contrast, Hyd-1 is active for H oxidation under more oxidizing conditions and cannot function in reverse. Importantly, Hyd-1 isO tolerant and can oxidize H in the presence of air, whereas Hyd-2 is ineffective for H oxidation under aerobic conditions. The results have direct relevance for physiological roles of Hyd-1 and Hyd-2, which are expressed in different phases of growth. The properties that we report suggest distinct technological applications of these contrasting enzymes.
Lukey, M. J., Parkin, A., Roessler, M. M., Murphy, B. J., Harmer, J., Armstrong, F. A., Palmer, T., & Sargent, F. (2010). How Escherichia coli is equipped to oxidize hydrogen under different redox conditions. Journal of Biological Chemistry, 285(6), 3928-3938. https://doi.org/10.1074/jbc.M109.067751, https://doi.org/10.1074/jbc.A109.067751