Desulfovibrio vulgaris hydrogenase: a nonheme iron enzyme lacking nickel that exhibits anomalous EPR and Mössbauer spectra.

A purification procedure for the periplasmic hydrogenase from Desulfovibrio vulgaris ( Hildenborough , National Collection of Industrial Bacteria 8303) is reported. The purified hydrogenase has a specific activity of 4800 units per mg of protein. Plasma emission studies reveal that this highly active hydrogenase is free of nickel and contains 11 (+/- 1) nonheme iron atoms per molecule. A combined EPR and Mössbauer study indicates that the majority of the iron atoms are bound in the form of iron- sulfur clusters. Two ferredoxin-type [4Fe-4S] clusters have been identified that exhibit normal EPR and Mössbauer parameters; however, no trace of 3Fe cluster is detected by the Mössbauer measurement. In the presence of oxidants, cytochrome c3, and CO, anomalous EPR and Mössbauer spectra indicative of atypical nonheme iron centers are observed.