- Human phenylalanine hydroxylase is activated by H2O2: a novel mechanism for increasing the L-tyrosine supply for melanogenesis in melanocytes. Schallreuter, K.U., Wazir, U., Kothari, S., Gibbons, N.C., Moore, J., Wood, J.M. Biochem. Biophys. Res. Commun. (2004)