Escherichia coli hydrogenase 3 is a reversible enzyme possessing hydrogen uptake and synthesis activities |
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Authors: | Toshinari Maeda Viviana Sanchez-Torres Thomas K. Wood |
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Affiliation: | (1) Artie McFerrin Department of Chemical Engineering, Texas A & M University, 220 Jack E. Brown Building, College Station, TX 77843-3122, USA;(2) Department of Biology, Texas A & M University, College Station, TX 77843-3258, USA;(3) Zachry Department of Civil and Environmental Engineering, Texas A & M University, College Station, TX 77843-3136, USA |
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Abstract: | In the past, it has been difficult to discriminate between hydrogen synthesis and uptake for the three active hydrogenases in Escherichia coli (hydrogenase 1, 2, and 3); however, by combining isogenic deletion mutations from the Keio collection, we were able to see the role of hydrogenase 3. In a cell that lacks hydrogen uptake via hydrogenase 1 (hyaB) and via hydrogenase 2 (hybC), inactivation of hydrogenase 3 (hycE) decreased hydrogen uptake. Similarly, inactivation of the formate hydrogen lyase complex, which produces hydrogen from formate (fhlA) in the hyaB hybC background, also decreased hydrogen uptake; hence, hydrogenase 3 has significant hydrogen uptake activity. Moreover, hydrogen uptake could be restored in the hyaB hybC hycE and hyaB hybC fhlA mutants by expressing hycE and fhlA, respectively, from a plasmid. The hydrogen uptake results were corroborated using two independent methods (both filter plate assays and a gas-chromatography-based hydrogen uptake assay). A 30-fold increase in the forward reaction, hydrogen formation by hydrogenase 3, was also detected for the strain containing active hydrogenase 3 activity but no hydrogenase 1 or 2 activity relative to the strain lacking all three hydrogenases. These results indicate clearly that hydrogenase 3 is a reversible hydrogenase. |
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Keywords: | E. coli hydrogenase 3 Reversible hydrogenase Hydrogen production Hydrogen uptake |
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