Hydroxylated

Of proteins

Several other amino acids aside from proline are susceptible to hydroxylation, especially lysine, asparagine, aspartate, and histidine. Lysine may be hydroxylated on its δ-C atom, forming hydroxylysine (Hyl). Several endogenous proteins contain hydroxyphenylalanine and hydroxytyrosine residues. These residues are formed by hydroxylation of phenylalanine and tyrosine, a process in which the hydroxylation converts phenylalanine residues into tyrosine residues. Hydroxylation at C-3 of tyrosine gives 3,4- dihydroxyphenylalanine (DOPA), which is a precursor to hormones and can be converted into dopamine.