The activation of the periplasmic (NiFe) hydrogenase of Desulfovibrio gigas by carbon monoxide

The activation of the periplasmic (NiFe) hydrogenase from Desulfovibrio gigas by dihydrogen is a complex phenomenon involving both ‘slow’ and ‘fast’ reactions. Carbon monoxide, a competitive inhibitor of hydrogenase activity, is demonstrated to cause the slow activation nearly as well as dihydrogen. Carbon monoxide does not reduce the (NiFe) hydrogenase and the fast reductive activation is effected by deuterium in the exchange assay. In the presence of dithionite, which immediately reduces the redox centers of the (NiFe) hydrogenase, the slow activation is still essential to attain full activity. Thus, the slow non-reductive and fast reductive steps of the activation can occur in any sequence.