title: A quinonoid is an intermediate of oxidative deamination reaction catalyzed by Dopa decarboxylase.
abstract: The reactions of Dopa decarboxylase (DDC) with l- and d-enantiomers of tryptophan methyl ester are described. Although both the enantiomers bind to the active site of the enzyme with similar affinity, their binding modes are different. l-enantiomer binds in an unproductive mode, while d-enantiomer acts as an oxidative deamination substrate. For the first time a quinonoid has been detected as intermediate of this reaction. By using rapid-scanning stopped-flow kinetic technique rate constants for formation and decay of this species have been determined. All these data, besides validating the functional DDC active site model, represent an important step toward the elucidation of the catalytic pathway of oxidative deamination.
authors.affiliation: Dipartimento di Scienze Neurologiche e della Visione, Sezione di Chimica Biologica, Università di Verona, Italy.
authors.forename: Mariarita
authors.initials: M
authors.lastname: Bertoldi
authors.forename: Barbara
authors.initials: B
authors.lastname: Cellini
authors.forename: Bruno
authors.initials: B
authors.lastname: Maras
authors.forename: Carla Borri
authors.initials: CB
authors.lastname: Voltattorni
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003641:Deamination; D004296:Dopa Decarboxylase / Q000737:chemistry / Q000378:metabolism*; D008968:Molecular Conformation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011809:Quinones / Q000737:chemistry / Q000378:metabolism; D015203:Reproducibility of Results; D013552:Swine; D014364:Tryptophan / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D011809:Quinones; C028129:tryptophan methyl ester; D014364:Tryptophan; D004296:Dopa Decarboxylase