Citation

García Moreno M, Varon R, Sánchez Gracia A, Tudela J, García Cánovas F. Biochim. Biophys. Acta 1994; 1205(2): 282-288.

Copyright

(Copyright © 1994, Elsevier Publishing)

DOI

10.1016/0167-4838(94)90246-1

PMID

8155710

Abstract

This paper presents a new reaction mechanism for the effect of the pH on the suicide inactivation of the diphenolase activity of tyrosinase. The applicability of the mechanism is supported by the experimental characterization of the kinetic behaviour of the frog epidermis enzyme acting on catechol, L-dopa and alpha-methyldopa at several pH values. Two enzyme froms 'met-' and 'oxy-' tyrosinase, but no their corresponding enzyme-diphenol complexes, present one ionizable group with very similar value of Ka which has been determined. The highest values of catalytic and inactivation efficiencies correspond to alpha-methyldopa and catechol, respectively. These kinetic studies have been carried out by using the transient phase approach previously developed, with negligible substrate consumption during the assay time. That illustrate the usefulness of the method for multisubstrate enzyme reactions.

Language: en

Keywords

Animals; Catechols; Enzyme Stability; Epidermis; Hydrogen-Ion Concentration; Kinetics; Levodopa; Methyldopa; Models, Biological; Monophenol Monooxygenase; Ranidae