title: Proposal for the mechanism of action of urocanase. Inference from the inhibition by 2-methylurocanate.
abstract: Incubation of urocanase with 2-methylurocanate leads, after an initial normal reaction, to a time dependent inactivation of the enzyme. It is suggested that a tautomeric form of the product, 2-methyl-imidazolone propionate, is the actual inhibitor. On the basis of these and of published experimental data a novel mechanism is proposed for the urocanase reaction. The crucial and initial step is the electrophilic addition of enzyme-bound NAD to the 2-position of the imidazole nucleus of urocanate.
mesh_terms: D006836:Hydro-Lyases / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D011485:Protein Binding; D011549:Pseudomonas / Q000201:enzymology; D014559:Urocanate Hydratase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014560:Urocanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D007093:Imidazoles; C053126:2-methylurocanic acid; D006836:Hydro-Lyases; D014559:Urocanate Hydratase; D014560:Urocanic Acid