Analysis and interpretation of the action mechanism of mushroom tyrosinase on monophenols and diphenols generating highly unstable o-quinones

Fenoll, Lorena G.; Rodrı́guez-López, José Neptuno; Garcı́a-Sevilla, Francisco; Garcı́a-Ruiz, Pedro Antonio; Varón, R.; Garcı́a-Cánovas, Francisco; Tudela, José

doi:10.1016/s0167-4838(01)00207-2

Cited by 135 publications

(98 citation statements)

References 50 publications

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“…This is a different behavior from that of the other monophenols studied and is not consistent with the MichaelisMenten kinetics model. This has been reported before by Ros et al [30] and Fennol et al [35], who related this behavior to both the suppressed autoactivation of tyrosinase from met to oxy form caused by binding of monophenols to the met form of the enzyme together with the high stability of quinone products.…”

Section: Resultssupporting

confidence: 73%

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Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

et al. 2012

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Despite the broad use of enzymes in electroanalytical biosensors, the influence of enzyme kinetics on the function of prototype sensors is often overlooked or neglected. In the present study, we employ amperometry as an alternative or complementary method to study the kinetics of tyrosinase, whose catalytic activity results in o-quinone products. We further compare our results for four monophenolic substrates with those obtained from ultravioletvisible spectrophotometry and show that the results from both assays are in good agreement. We also observe large variations in the enzyme kinetics for different monophenolic substrates depending on the R-group at the para position. To further study this effect, we investigate the stability of quinone products in the enzymatic assay. This information can in principle be utilized to discriminate between different phenolic species by monitoring the reaction rate.

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Section: Resultssupporting

confidence: 73%

“…Quinones are known to be unstable and undergo several non-enzymatic reactions [29,35]. Here, we study the stability of the biocatalytic product of tyrosinase reaction with monophenolic substrates by following the evolution of their UV-Vis absorption spectra.…”

Section: Stability Of O-quinonesmentioning

confidence: 99%

Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

et al. 2012

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“…The enzyme catalyzes the oxygenation of phenols to catechols by oxygen (so-called phenolase activity) as well as the dehydrogenation of catechols to the corresponding o-quinones (catecholase activity) [18]. These latter products are unstable in aqueous solution and undergo further non-enzymatic processes to form melanin-like stable compounds [19]. Tyrosinase exhibits also a substrate inhibition effect (suicide inactivation) when acting on o-diphenols [20,21].…”

Section: G a L L E Y P R O O Fmentioning

confidence: 99%

Oxidation of oleuropein studied by EPR and spectrophotometry

Tzika

Papadimitriou

Sotiroudis

et al. 2008

Euro J Lipid Sci & Tech

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The autoxidation at alkaline pH and enzymatic oxidation by mushroom tyrosinase of oleuropein, the dominant biophenol present in the fruits and leaves of Olea europea, was followed by both electron paramagnetic resonance (EPR) and absorption spectroscopy. For comparison, the same oxidation processes were applied to 4-methylcatechol, a simple polyphenol present in olive mill wastewaters. EPR spectra of stable o-semiquinone radicals produced during autoxidation at pH 12 and short-lived o-semiquinone free radicals produced during autoxidation at pH 9.0 or tyrosinase action and stabilized by chelation with a diamagnetic metal ion (Mg 21 ) were recorded for both polyphenols, and the corresponding hyperfine splitting constants were determined. The UV-Vis spectral characteristics of the oxidation of polyphenols were highly dependent on the type of polyphenol, oxidant type and the pH of the reaction. The kinetic behavior of tyrosinase in the presence of oleuropein and 4-methylcatechol was followed by recording spectral changes at 400 nm (absorption maximum) over time. The tysosinase activity with oleuropein showed a pronounced pH optimum at pH 6.5 and a minor one around pH 8. From the data analysis of the initial rate at pH 6.5, the kinetic parameters K m = 0.34 6 0.03 mM and V max = (0.029 6 0.002) DA 400 min -1 were determined for oleuropein.

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“…Active sites of tyrosinase have three different states of binuclear copper structure ( Figure 1): met-tyrosinase (E met ), deoxy-tyrosinase (E deoxy ), and oxy-tyrosinase (E oxy ) 19 . Both oxy-tyrosinase and met-tyrosinase can act in catecholase activity while only oxy-tyrosinase is able to catalyze monophenols to odiphenols, and binding of monophenol to met-tyrosinase will inactivate tyrosinase 20 . Browning after harvest is a common phenomenon in crops such as mushrooms, which decreases the commercial value of the product.…”

Section: Introductionmentioning

confidence: 99%

Potent inhibitory effects of benzyl and p-xylidine-bis dithiocarbamate sodium salts on activities of mushroom tyrosinase

Amin

Saboury

Mansuri-Torshizi

et al. 2010

Journal of Enzyme Inhibition and Medicinal Chemistry

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Analysis and interpretation of the action mechanism of mushroom tyrosinase on monophenols and diphenols generating highly unstable o-quinones

Cited by 135 publications

References 50 publications

Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

Oxidation of oleuropein studied by EPR and spectrophotometry

Potent inhibitory effects of benzyl and p-xylidine-bis dithiocarbamate sodium salts on activities of mushroom tyrosinase

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