Action of tyrosinase on hydroquinone in the presence of catalytic amounts of o-diphenol. A kinetic study

García-Molina, Maria del Mar; Berná, José; Muñoz‐Muñoz, José Luis; Garcı́a-Ruiz, Pedro Antonio; Moreno, Manuela García; Martínez, José Rodríguez; Garcı́a-Cánovas, Francisco

doi:10.1007/s11144-014-0723-1

Cited by 19 publications

(26 citation statements)

References 36 publications

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“…and Supporting Information Fig. 1SI suggests that this compound is another alternative substrate of tyrosinase , rather than inhibitor or inactivator. It was therefore decided to test the possible activity of tyrosinase on BR.…”

Section: Resultsmentioning

confidence: 96%

“…In this way, the characteristic lag period of the monophenolase activity which complicates the measurement of the V 0 was eliminated. This quantity is given by the equation Finally, the activity of tyrosinase on BR as substrate was measured in the presence of (a) ascorbic acid, (b) hydrogen peroxide, and (c) catalytic concentrations of TBC and NADH as reductant to maintain the concentration of o-diphenol constant in the medium, ensuring the continuous generation of the enzymatic form E ox (17)(18)(19). Recordings were made at 480 nm, the wavelength at which the quinone of BR absorbs.…”

Section: Figmentioning

confidence: 99%

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4-n-butylresorcinol, a depigmenting agent used in cosmetics, reacts with tyrosinase

et al. 2016

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4-n-Butylresorcinol (BR) is considered the most potent inhibitor of tyrosinase, which is why it is used in cosmetics as a depigmenting agent. However, this work demonstrates that BR is a substrate of this enzyme. The E m (met-tyrosinase) form is not active on BR, but E ox (oxy-tyrosinase) can act on this molecule, hydroxylating it to o-diphenol. In turn, this is oxidized to an oquinone, which isomerizes to a red p-quinone. Thus, for tyrosinase to act on this compound, a mechanism to generate E ox in the medium is required, which can be achieved by means of hydrogen peroxide or ascorbic acid. A kinetic analysis of the proposed mechanism allows its kinetic characterization: catalytic constant k BR cat (8.49 6 0.20 s 21 ) and Michaelis-constant K BR M (60.26 6 8.76 lM). These findings are compared with those for other monophenolic substrates of tyrosinase. Studies of BR docking to the E m form of the enzyme show that the hydroxyl group in C-1 position is oriented toward the copper atom A (CuA), as in it is L-tyrosine. As regards E ox , BR is oriented with the carbon in C-6 position ready to be hydroxylated. The reaction of BR originates o-quinones, which isomerize to p-quinones, which in turn, could react with thiol compounds, a finding that could have important implications for pharmacology and the cosmetic industry. , initial p-quinone formation rate; V p2Q max , maximum action rate of tyrosinase on 4-n-butylresorcinol

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Section: Resultsmentioning

confidence: 96%

Section: Figmentioning

confidence: 99%

4-n-butylresorcinol, a depigmenting agent used in cosmetics, reacts with tyrosinase

et al. 2016

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“…Their different behavior in both activities , the structure of the compound of interest and identification of its analogous resveratrol as a substrate of the enzyme , suggested that the oxyresveratrol could also be considered as a substrate. The enzyme could hydroxylase this molecule in ortho position to the hydroxyl of the ring in 4′ position, producing an o ‐diphenol which is oxidized to an o ‐quinone that finally isomerizes to p ‐quinone, as in the case of hydroquinone . Therefore, we proceeded to the study of the oxyresveratrol as a possible substrate of the enzyme.…”

Section: Resultsmentioning

confidence: 99%

“…Inset, recording a). For the enzyme to act on this kind of molecules, the enzymatic form E m must become E ox , and this can happen by adding a catalytic quantity of o ‐diphenol to the medium, which will reduce the E m (the o ‐diphenol must remain constant, for which reason ascorbic acid is also added) , or by adding another kind of substrate of the enzyme, such as hydrogen peroxide, or ascorbic acid .…”

Section: Resultsmentioning

confidence: 99%

“…Our studies on the mechanisms of action of tyrosinase show that for the enzyme to show monophenolase activity, the following must be present: ( a ) hydrogen peroxide (H 2 O 2 ), which allows the enzyme form E m (met‐tyrosinase) to become E ox , which is active on monophenols, ( b ) a reductant as ascorbic acid (AH 2 ) that is able to transform E m into E d (deoxy‐tyrosinase), which, with oxygen, produces the E ox form, and ( c ) catalytic quantities of o ‐diphenol (to bring about the transformation of E m into E d , which, with oxygen, becomes E ox ) and ascorbic acid to keep the quantity of o ‐diphenol constant in the reaction medium and so that E ox does not cease to be generated . Consequently, in the presence of hydrogen peroxide, the enzyme showed activity toward a series of monophenols traditionally described as inhibitors .…”

Section: Introductionmentioning

confidence: 99%

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Kinetic characterization of oxyresveratrol as a tyrosinase substrate

et al. 2015

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Oxyresveratrol is a stilbenoid described as a powerful inhibitor of tyrosinase and proposed as skin-whitening and anti-browning agent. However, the enzyme is capable of acting on it, considering it as a substrate, as it has been proved in the case of its analogous resveratrol. Tyrosinase hydroxylates the oxyresveratrol to an odiphenol and oxidizes the latter to an o-quinone, which finally isomerizes to p-quinone. For these reactions to take place the presence of the E ox (oxy-tyrosinase) form is necessary. The kinetic analysis of the proposed mechanism has allowed the kinetic characterization of this molecule as a substrate of tyrosinase, affording a catalytic constant of 5.

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Catalytic mechanism of tyrosinases

Zolghadri,

Saboury

2024

The Enzymes

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Action of tyrosinase on hydroquinone in the presence of catalytic amounts of o-diphenol. A kinetic study

Cited by 19 publications

References 36 publications

4-n-butylresorcinol, a depigmenting agent used in cosmetics, reacts with tyrosinase

4-n-butylresorcinol, a depigmenting agent used in cosmetics, reacts with tyrosinase

Kinetic characterization of oxyresveratrol as a tyrosinase substrate

Catalytic mechanism of tyrosinases

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