Multicopper oxidase involved in copper homeostasis and copper tolerance under aerobic conditions. Is responsible for the oxidation of Cu(+) to the less harmful Cu(2+) in the periplasm, thereby preventing Cu(+) from entering the cytoplasm. 4 Cu(+) + 4 H(+) + O2 = 4 Cu(2+) + 2 H2O Binds 4 Cu cations per monomer. Monomer. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the multicopper oxidase family.