Copper-containing amine oxidase contains a covalently bound organic cofactor, 2, 4, 5-trihydroxyphenylalanine (topa) quinone, which is formed by post-translational modification of a specific tyrosine residue in the presence of copper ion and oxygen molecule. Apo-enzyme crystals were anaerobically soaked in the mother liquor that contains copper ion and were freeze-trapped to determine the initial structure of the biogenesis. In order to see the structures in the following stages, we started the reaction by exposing the copper-bound crystals to the air, and freeze-trapped them immediately, and also trapped long after the exposure. The structures of three district intermediates have been determined. The molecular mechanism of the topa quinone biogenesis will be discussed on the basis of these X-ray snapshots.
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