Structure and mechanism of tryptophylquinone enzymes.

Tryptophylquinone cofactors are formed by posttranslational modifications that result in the incorporation of two oxygens into a tryptophan side chain, and the covalent cross-linking of that side chain to another amino acid residue. Tryptophylquinone enzymes catalyze the oxidative deamination of primary amines, and utilize other redox proteins as electron acceptors. Mechanistic and structural studies of these enzymes are providing insight into how these enzymes utilize these highly reactive protein-derived quinones in a controlled manner to facilitate biologically important catalytic and electron transfer reactions.