“…In contrast to the rapidly increasing information on the involvement of the metal in the binding and activation of oxygen in these copper proteins (Eickman et al, 1979;Brown et al, 1980; Himmelwright et al, 1980), the knowledge of the part played by the protein moiety especially with regard to the metal ligands and the active-site residues is still limited. Although a number of investigations implicate the involvement of histidyl residues as metal ligands of the active-site copper (Salvato et al, 1974;Tallandini et al, 1975;Engelborghs & Lontie, 1973;Gutteridge et al, 1977) , progress has been hampered by the complexity and molecular heterogeneity of these molecules. In this report, the residues of the active-site region of Neurospora tyrosinase were identified by chemical modification employing dye-sensitized photooxidation.…”