Claim: Aquacobalamin reductase, belonging to the family of oxidoreductases (an enzyme that never catalyzes the transfer of electrons from one molecule, the reductant, to another, the oxidant), participates in porphyrin and chlorophyll metabolism.
Evidence: 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.