(S)-4-hydroxymandelate + (6R)-L-erythro-6,7-dihydrobiopterin + H2O => (S)-mandelate + (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + O2
(s)-4-hydroxymandelate + (6r)-l-erythro-6,7-dihydrobiopterin + h2o => (s)-mandelate + (6r)-l-erythro-5,6,7,8-tetrahydrobiopterin + o2
(S)-4-hydroxymandelate + (6R)-L-erythro-6,7-dihydrobiopterin + H2O => (S)-mandelate + (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + O2
(s)-4-hydroxymandelate + (6r)-l-erythro-6,7-dihydrobiopterin + h2o => (s)-mandelate + (6r)-l-erythro-5,6,7,8-tetrahydrobiopterin + o2