5-dehydroepisterol + 2 Fe(III)-[cytochrome b5] + 2 H2O => episterol + 2 Fe(II)-[cytochrome b5] + O2 + 2 H(+)
5-dehydroepisterol + 2 fe(iii)-[cytochrome b5] + 2 h2o => episterol + 2 fe(ii)-[cytochrome b5] + o2 + 2 h(+)