Sulfite reductases belong to the oxidoreductase (an enzyme that catalyzes the transfer of electrons from the reductant to the oxidant)  family, and participates in selenoamino acid metabolism and sulfur assimilation.
Sulfite reductases, which belong to the oxidoreductase family, are found in archaea, bacteria, fungi, and plants. In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This enzyme participates in selenoamino acid metabolism and sulfur assimilation. 
