Multicopper oxidase family

General Activity
Multicopper oxidases are enzymes which oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to a trinuclear copper center; dioxygen binds to the trinuclear center and, following the transfer of four electrons, is reduced to two molecules of water. There are three spectroscopically different copper centers found in multicopper oxidases: type 1 (or blue), type 2 (or normal) and type 3 (or coupled binuclear). The enzymes that belong to this family are laccases, L-ascorbate oxidases, and ceruloplasmin.

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. Among other, blood coagulation factor V (F5) and blood coagulation factor VIII (F8) are found.

In venom, orthologs have been described in three different snake species. They all act as cofactors in blood coagulation by mimicking the coagulation factor V. Once complexed with the venom catalytic subunit (a venom coagulation factor Xa-like), these proteins form the prothrombinase complex (prothrombin activator) and converts prothrombin to thrombin (Rao et al., 2002, Speijer et al., 1986).

Venom coagulation factor Va-like forms a non-covalently linked complex with the venom coagulation factor Xa-like. The interaction between the two chains is calcium-dependent.