Eukaryotic molybdopterin oxidoreductase (IPR008335)

Short name: Mopterin_OxRdtase_euk

Overlapping homologous superfamilies

Family relationships


A number of different eukaryotic oxidoreductases that require and bind a molybdopterin cofactor have been shown [PMID: 2015248] to share a few regions of sequence similarity. These enzymes include xanthine dehydrogenase (EC:, aldehyde oxidase (EC:, nitrate reductase (EC:, and sulphite oxidase (EC: The multidomain redox enzyme NAD(P)H:nitrate reductase (NR) catalyses the reduction of nitrate to nitrite in a single polypeptide electron transport chain with electron flow from NAD(P)H-FAD-cytochrome b5-molybdopterin-NO(3). Three forms of NR are known, an NADH-specific enzyme found in higher plants and algae (EC:; an NAD(P)H-bispecific enzyme found in higher plants, algae and fungi (EC:; and an NADPH-specific enzyme found only in fungi (EC: [PMID: 2204158]. The mitochondrial enzyme sulphite oxidase (sulphite:ferricytochrome c oxidoreductase; EC: catalyses oxidation of sulphite to sulphate, using cytochrome c as the physiological electron acceptor. Sulphite oxidase consists of two structure/function domains, an N-terminal haem domain, similar to cytochrome b5; and a C-terminal molybdopterin domain [PMID: 2687265].

Despite functional parallels, members of the family show no sequence similarity to the C-terminal molybdopterin domain of xanthine dehydrogenase, although xanthine dehydrogenase, nitrate reductases and sulphite oxidase all contain the eukaryotic molybdopterin oxidoreductases signature. Sequence comparison suggests that only a single Cys residue (Cys186 in chicken sulphite oxidase), is invariant in all these enzymes, indicating that it may play a role in binding molybdopterin to the protein [PMID: 2249998, PMID: 7896804].

GO terms

Biological Process

GO:0055114 oxidation-reduction process

Molecular Function

GO:0016491 oxidoreductase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.