Slow-Binding Inhibition of Mushroom (Agaricus b isporus) Tyrosinase Isoforms by Tropolone

A kinetic study of the inhibition of mushroom tyrosinase by tropolone has been made. Three tyrosinase isoforms were used:  two commercial tyrosinases from Fluka and Sigma (isoelectric points of 4.3 and 4.1, respectively) and one purified isoform from mushroom strain U1 (isoelectric point of 4.5). Tr...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 1999-07, Vol.47 (7), p.2638-2644
Main Authors: Espín, Juan Carlos, Wichers, Harry J
Format: Article
Language:English
Subjects:
Agaricales - enzymology
Agaricus bisporus
Agrotechnological Research Institute
binding
Biological and medical sciences
browning
catechol oxidase
enzyme inhibitors
Enzyme Inhibitors - metabolism
Enzyme Inhibitors - pharmacology
Food industries
Fruit and vegetable industries
Fundamental and applied biological sciences. Psychology
inhibition
Instituut voor Agrotechnologisch Onderzoek
Isoenzymes - antagonists & inhibitors
Isoenzymes - metabolism
Kinetics
mushrooms
Protein Binding
Substrate Specificity
tropolone
Tropolone - metabolism
Tropolone - pharmacology
Tyrosine - antagonists & inhibitors
Tyrosine - metabolism
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Summary:A kinetic study of the inhibition of mushroom tyrosinase by tropolone has been made. Three tyrosinase isoforms were used:  two commercial tyrosinases from Fluka and Sigma (isoelectric points of 4.3 and 4.1, respectively) and one purified isoform from mushroom strain U1 (isoelectric point of 4.5). Tropolone is a slow-binding inhibitor of these mushroom tyrosinase isoforms. Increasing tropolone concentrations provoked a progressive decrease in both the initial velocity and the final (inhibited) steady-state rate in the progress curves of product accumulation. A rapid formation of an enzyme−inhibitor complex, which further undergoes a slow reversible reaction, could take place since the inhibition of the different isoforms was partially reversed by the addition of CuSO4. The kinetic parameters that described the inhibition by tropolone were evaluated by nonlinear regression fits. Incubation experiments of the different isoforms with tropolone demonstrated that this inhibitor only could bind to the “oxy” form of tyrosinase which justifies a mechanism previously proposed to explain the inhibition of tyrosinase by slow-binding inhibitors. Keywords: Agaricus; inhibition; mushroom; slow-binding; tropolone; tyrosinase
ISSN:0021-8561
1520-5118
DOI:10.1021/jf981055b