title: Stereospecific inactivation of tyrosinase by L- and D-ascorbic acid.
abstract: A kinetic study of the inactivation of tyrosinase by L- and D-ascorbic acid isomers has been carried out. In aerobic conditions, a suicide inactivation mechanism operates, which was attributed to the enzymatic form oxytyrosinase. This suicide inactivation is stereospecific as regards the affinity of the enzyme for the substrate but not as regards the speed of the process, which is the same for both isomers, reflecting the influence of the chemical shift of the carbon C-2 (delta(2)) and C-3 (delta(3)) as seen by (13)C-NMR. The inactivation of deoxytyrosinase and mettyrosinase observed in anaerobic conditions, is irreversible and faster than the suicide inactivation process, underlining the fact that the presence of oxygen protects the enzyme against inactivation.
authors.affiliation: Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Universidad de Murcia, E-30100, Espinardo, Murcia, Spain.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Munoz-Munoz
authors.forename: Francisco
authors.initials: F
authors.lastname: Garcia-Molina
authors.forename: Pedro Antonio
authors.initials: PA
authors.lastname: García-Ruiz
authors.forename: Ramon
authors.initials: R
authors.lastname: Varon
authors.forename: Jose
authors.initials: J
authors.lastname: Tudela
authors.forename: Francisco
authors.initials: F
authors.lastname: García-Cánovas
authors.forename: Jose Neptuno
authors.initials: JN
authors.lastname: Rodriguez-Lopez
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D014442:Monophenol Monooxygenase; D001205:Ascorbic Acid; D010100:Oxygen