1.3.99.33	dihydrourocanate + acceptor = urocanate + reduced acceptor	-	-	
1.3.99.33	dihydrourocanate + acceptor = urocanate + reduced acceptor	reaction mechanism, overview. Apo-ADP enzyme represents an inactive state, while the binding of FAD induces movement of the clamp domain that enables binding of the substrate urocanate to form an active complex with a solvent-accessible channel for water-mediated proton delivery to Arg411, and subsequent protonation of the substrate. Once urocanate is reduced to imidazole propionate, Arg411 turns away accompanied by conformational changes, resulting in closure of the solvent-accessible channel by the hydrophobic lid and release of imidazole propionate, allowing for a new substrate molecule to enter the active site. Binding is entropically driven for both urocanate and imidazole propionate	763503