Tyrosine Formation from Phenylalanine by Ultraviolet Irradiation

抄録

When phenylalanine was irradiated at ultraviolet (UV) light, p-tyrosine, m-tyrosine and o-tyrosine were identified as hydroxylated products. From p-tyrosine and m-tyrosine, the formation of L-3, 4-dihydroxyphenylalanine (DOPA) was obsered. The hydroxylation of phenylalanine was prevented by radical scavengers, e.g., catalase, superoxide dismutase, sodium thiocyanate, mannitol, potassium iodide and thiourea. Replacement of air with nitrogen gas prevented the hydroxylation, but did not depress it completely. The addition of H₂O₂ increased significantly the hydroxylation of phenylalanine. These results suggest that the hydroxylation of phenylalanine by UV irradiation may be caused by ·OH formed during the decomposition of H₂O.