Electron transfer between hydrogenases and mono- and multiheme cytochromes in Desulfovibrio ssp

A comparative study of electron transfer between the 16 heme high molecular mass cytochrome (Hmc) from Kesulfovibrio vulgaris Hildenborough and the [Fe] and [NiFe] hydrogenases from the same organism was carried out, both in the presence and in the absence of catalytic amounts of cytochrome Cg. For comparison, this study was repeated with the [NiFe] hydrogenase from D. gigas. Hmc is very slowly reduced by the [Fe] hydrogenase, but faster by either of the two [NiFe] hydrogenases. In the presence of cytochrome c(3), in equimolar amounts to the hydrogenases, the rates of electron transfer are significantly increased and are similar for the three hydrogenases. The results obtained indicate that the reduction of Hmc by the [Fe] or [NiFe] hydrogenases is most likely mediated by cytochrome c(3). A similar study with D. vulgaris Hildenborough cytochrome C-553 shows that, in contrast, this cytochrome is reduced faster by the [Fe] hydrogenase than by the [NiFe] hydrogenases. However, although catalytic amounts of cytochrome c3 have no effect in the reduction by the [Fe] hydrogenase, it significantly increases the rate of reduction by the [NiFe] hydrogenases.