The three classes of hydrogenases from sulfate-reducing bacteria of the genus Desulfovibrio

Abstract

Three types of hydrogenases have been isolated from the sulfate-reducing bacteria of the genus Desulfobibrio. They differ in their subunit and metal compositions, physico-chemical characteristics, amino acid sequences, immunological ractivities, gene structures and their catalytic properties. Broadly, the hydrogenases can be considered as ‘iron only’ hydrogenases and nickel-containing hydrogenases. The iron-sulfur-containg hydrogenase ([Fe] hydrogenase) contains two ferredoxin-type (4Fe-4S) clusters and an atypical iron-sulfur center belived to be involved in the activation of H 2. The [Fe] hydrogenase has the highest specific activity in the evolution and consumption of hydrogen and in the proton-deuterium exchange reaction and this enzyme is the most sensitive to CO and NO 2 −. It is not present in all species of Desulfovibrio The nickel-(iron-sulfur)-containing hydrogenases ([NiFe] hydrogenase) posses two (4Fe-4S) centers and one (3Fe- xS) cluster in addition to nickel and have been found in all species of Desulfovibrio so far investigated. The redox active nickel is ligated by at least two cysteinyl thiolate residues and the [NiFe] hydrogenases are particularly resistant to inhibitors such as CO and NO 2 −. The genes encoding the large and small subunits of a periplasmic and a membrane-bound species of the [NiFe] hydrogenase have been cloned in Eschierichia (E.) coli and sequenced. Their derived amino acid sequences exhibit a high degree of homology (70%); however, they show no obvious metal-binding sites or homology with the derived amino acid sequence of the [Fe] hydrogenase. The third class is represented by the nickel-iron-sulfur)-selenium-containing hydrogenases ([NiFe-Se] hydrohenases) which contain nickel and selenium in equimoleular amounts plus (4Fe-4S) centers and are only found in some species of Desulfovibrio. The genes encoding the large and small subunits of the periplasmic hydrogenase from Desulfrovibio (D) baculatus (DSM 1743) (for abbrviations see appendix) have been cloned