The crystal structures of F2-Tyr272 and Cl2-Tyr272 GAOV reveal C-F and C-Cl bond cleavages in the Cu-bound crosslinked cofactor. (A) The omit Fo-Fc electron densities (blue, 4.0 σ) and the cross-linked form F2-Tyr272 GAOV. The fluorine atom was highlighted in purple. (B) The omit Fo-Fc electron densities (blue, 4.0 σ) and the cross-linked form of Cl2-Tyr272 GAOV active site. The chlorine atom was colored in mint. (C) Comparison of the active sites of all three structures. The active site of F2-Tyr272 GAOV, Cl2-Tyr272 GAOV, GAOV are shown in green, pink, and grey, respectively. WAT represents the water ligand bound at the Cu(II) center. (D) The active site interaction diagrams of F2-Tyr272 GAOV, and Cl2-Tyr272 GAOV, and GAOV.