Erythromycin 12 hydroxylase (EC 1.14.13.154, EryK) is an enzyme with systematic name erythromycin-D,NADPH:oxygen oxidoreductase (12-hydroxylating) . This enzyme catalyses the following chemical reactionerythromycin D + NADPH + H+ + O2 erythromycin C + NADP+ + H2O