<p> Dissimilatory sulphite reductase catalyzes the six-electron reduction of sulphite to sulphide, as the terminal reaction in dissimilatory sulphate reduction. It remains unclear however, whether trithionate and thiosulphate serve as intermediate compounds to sulphide, or as end products of sulphite reduction [<cite idref="PUB00015467"/>]. Sulphite reductase is a multisubunit enzyme composed of dimers of either alpha/beta or alpha/beta/gamma subunits, each containing a siroheme and iron sulphur cluster prosthetic centre [<cite idref="PUB00009960"/>]. Found in sulphate-reducing bacteria, these genes are commonly located in a unidirectional gene cluster [<cite idref="PUB00015468"/>].</p> Sulphite reductase, dissimilatory-type alpha subunit