The second cupredoxin domain of plant Ascorbate oxidase homologs
This family includes plant laccases similar to ascorbate oxidase. Ascorbate oxidase catalyzes the oxidation of ascorbic acid to dehydroascorbic acid. It can detect levels of ascorbic acid and eliminate it. The biological function of ascorbate oxidase is still not clear. Ascorbate oxidase belongs to multicopper oxidase (MCO) family which couples oxidation of substrates with reduction of dioxygen to water. Although MCOs have diverse functions, majority of them have three cupredoxin domain repeats that include one mononuclear and one trinuclear copper center. The copper ions are bound in several sites: Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster. MCOs oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to the active site trinuclear copper center. The cupredoxin domain 2 of 3-domain MCOs has lost the ability to bind copper.
Jiyao W et al.(2023). "The conserved domain database in 2023.",