May be involved in cell growth. Probably acts as a terminal oxidase of plasma electron transport from cytosolic NAD(P)H via hydroquinones to acceptors at the cell surface. Hydroquinone oxidase activity alternates with a protein disulfide-thiol interchange/oxidoreductase activity which may control physical membrane displacements associated with vesicle budding or cell enlargement. The activities oscillate with a period length of 22 minutes and play a role in control of the ultradian cellular biological clock (By similarity). Inhibited by the antitumor sulfonylurea LY181984, the vabilloid capsaicin, and retinoids. Extracellular and plasma membrane-associated. Glycosylated. Belongs to the ENOX family.