Stereospecific inactivation of tyrosinase by L- and D-ascorbic acid.
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.
Munoz-Munoz
Jose Luis
JL
Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Universidad de Murcia, E-30100, Espinardo, Murcia, Spain.
Garcia-Molina
Francisco
F
García-Ruiz
Pedro Antonio
PA
Varon
Ramon
R
Tudela
Jose
J
García-Cánovas
Francisco
F
Rodriguez-Lopez
Jose Neptuno
JN
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
D014442:Monophenol Monooxygenase; D001205:Ascorbic Acid; D010100:Oxygen