Plasma membrane ferroxidase that mediates the extracellular conversion of ferrous/Fe(2+) iron into its ferric/Fe(3+) form. Couples ferroportin which specifically exports ferrous/Fe(2+) iron from cells to transferrin that only binds and shuttles extracellular ferric/Fe(3+) iron throughout the body. By helping iron transfer from cells to blood mainly contributes to dietary iron absorption by the intestinal epithelium and more generally regulates iron levels in the body