Multicopper oxidase
Class of enzymes
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In molecular biology, multicopper oxidases are enzymes which oxidise their substrate by accepting electrons at a mononuclear copper centre and transferring them to a trinuclear copper centre; dioxygen binds to the trinuclear centre and, following the transfer of four electrons, is reduced to two molecules of water.[1] There are three spectroscopically different copper centres found in multicopper oxidases: type 1 (or blue), type 2 (or normal) and type 3 (or coupled binuclear).[2][3] Multicopper oxidases consist of 2, 3 or 6 of these homologous domains, which also share homology with the cupredoxins azurin and plastocyanin. Structurally, these domains consist of a cupredoxin-like fold, a beta-sandwich consisting of 7 strands in 2 beta-sheets, arranged in a Greek-key beta-barrel.[4]
| Multicopper oxidase (type 1) | |||||||
|---|---|---|---|---|---|---|---|
crystal structures of e. coli laccase cueo under different copper binding situations | |||||||
| Identifiers | |||||||
| Symbol | Cu-oxidase | ||||||
| Pfam | PF00394 | ||||||
| Pfam clan | CL0026 | ||||||
| InterPro | IPR001117 | ||||||
| PROSITE | PDOC00076 | ||||||
| SCOP2 | 1aoz / SCOPe / SUPFAM | ||||||
| Membranome | 253 | ||||||
| |||||||
The family of multicopper oxidases can be divided into three groups based on the electron-donating substrate. [5] Laccases oxidize a variety of organic substrates, metalloxidases accept metal substrates and a third group contains multicopper oxidases that are specific towards one single substrate. Multicopper oxidases include:
- Ceruloplasmin EC 1.16.3.1 (ferroxidase), a 6-domain enzyme found in the serum of mammals and birds that oxidizes different inorganic and organic substances; exhibits internal sequence homology that appears to have evolved from the triplication of a Cu-binding domain similar to that of laccase and ascorbate oxidase.
- Laccase EC 1.10.3.2 (urishiol oxidase), a 3-domain enzyme found in fungi and plants, which oxidizes different phenols and diamines. CueO is a laccase found in Escherichia coli that is involved in copper-resistance.[4]
- Ascorbate oxidase EC 1.10.3.3, a 3-domain enzyme found in higher plants.
- Nitrite reductase EC 1.7.2.1, a 2-domain enzyme containing type-1 and type-2 copper centres.[6][7]
In addition to the above enzymes there are a number of other proteins that are similar to the multi-copper oxidases in terms of structure and sequence, some of which have lost the ability to bind copper. These include: copper resistance protein A (copA) from a plasmid in Pseudomonas syringae; domain A of (non-copper binding) blood coagulation factors V (Fa V) and VIII (Fa VIII);[8] yeast Fet3p (FET3) required for ferrous iron uptake;[9] yeast hypothetical protein YFL041w; and the fission yeast homologue SpAC1F7.08.