Characterization of Escherichia coli [NiFe]-hydrogenase distribution during fermentative growth at different pHs

The contribution made by each of the three active [NiFe]-hydrogenases (Hyd) of Escherichia coli during fermentation of glucose or glycerol in peptone-based medium at different pHs was analysed. The activities of the hydrogen-oxidizing Hyd-1 and Hyd-2 enzymes showed a reciprocal dependence on the pH of the medium while Hyd-3, a key component of the hydrogen-evolving formate hydrogenlyase complex, was mainly active at pH 6.5. Our findings identify the conditions during fermentation of glucose or glycerol under which each [NiFe]-hydrogenase is optimally active and demonstrate a previously unrecognized dependence on Hyd-1 activity at low pH.