Function
A bifunctional enzyme that catalyzes the reduction of elemental sulfur or polysulfide to hydrogen sulfide with NADPH as electron donor. Also functions as a reduced ferredoxin:NADP oxidoreductase with a very high affinity for reduced ferredoxin. Exhibits a broad specificity for various physiological and non-physiological substrates with varied reduction potentials such as methyl viologen, benzyl viologen, FAD, FMN, methylene blue, 2,6-dichlorophenolindophenol (DCIP), cytochrome C and ferricyanide with highest preference for benzyl viologen. Does not reduce fumarate, succinate, nitrate, nitrite, sulfate, sulfite or protons. Does not possess any hydrogenase activity or NADPH-dependent glutamate synthase activity.