Tyrosinase: kinetic analysis of the transient phase and the steady state

Ros, JoséRamón; Rodríguez-López, JoséNeptuno; Garcı́a-Cánovas, Francisco

doi:10.1016/0167-4838(94)90029-9

Cited by 106 publications

(164 citation statements)

References 25 publications

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“…Hence, the former predicts that there is no inhibition caused by excess of monophenol (Figure 3), which agrees with the mechanism of Scheme I. Experiments carried out with tyrosinase from other sources (frog skin [18], apple [19] and pear [20]) provided similar results). Equation (7), indicates that inhibition occurs at high monophenol concentrations.…”

Section: Effect Of Initial Monophenol and Enzyme Concentrations On Tysupporting

confidence: 76%

“…As has been demonstrated experimentally [4] and by simulating the reactions evolving according to the mechanism of Scheme l [18], the length of the lag period diminishes as [E] Figure 1.…”

Section: Effect Of Initial Monophenol and Enzyme Concentrations On Tymentioning

confidence: 80%

“…In addition, the kinetic analysis of the mechanism of Scheme l provides an analytical expression for V M;DC ss of the type [18]:…”

Section: Variation In Substrate Concentrationmentioning

confidence: 99%

See 2 more Smart Citations

Effect of tetrahydropteridines on the monophenolase and diphenolase activities of tyrosinase

Molina

Muñoz

Varón

et al. 2007

Journal of Enzyme Inhibition and Medicinal Chemistry

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This study explains the action of compounds such as 6-tetrahydrobiopterin, (6BH 4 ) and 6,7-dimethyltetrahydrobiopterin (6,7-di-CH 3 BH 4 ) on the monophenolase and diphenolase activities of tyrosinase. These reductants basically act by reducing the o-quinones, the reaction products, to o-diphenol. In the case of the diphenolase activity a lag period is observed until the reductant is depleted; then the system reaches the steady-state. In the action of the enzyme on monophenol substrates, when the reductant concentration is less than that of the o-diphenol necessary for the steady-state to be reached, the system undergoes an apparent activation since, in this way, the necessary concentration of o-diphenol will be reached more rapidly. However, when the reductant concentration is greater than that of the o-diphenol necessary for the steady-state to be reached, the lag period lengthens and is followed by a burst, by means of which the excess o-diphenol is consumed, the steady-state thus taking longer to be reached. Moreover, in the present kinetic study, we show that tyrosinase is not inhibited by an excess of monophenol, although, to confirm this, the system must be allowed to pass from the transition state and enter the steady-state, which is attained when a given amount of o-diphenol has accumulated in the medium.

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Section: Effect Of Initial Monophenol and Enzyme Concentrations On Tysupporting

confidence: 76%

“…As has been demonstrated experimentally [4] and by simulating the reactions evolving according to the mechanism of Scheme l [18], the length of the lag period diminishes as [E] Figure 1.…”

Section: Effect Of Initial Monophenol and Enzyme Concentrations On Tymentioning

confidence: 80%

See 1 more Smart Citation

Effect of tetrahydropteridines on the monophenolase and diphenolase activities of tyrosinase

Molina

Muñoz

Varón

et al. 2007

Journal of Enzyme Inhibition and Medicinal Chemistry

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“…Low concentrations of NADH The effects of low concentrations of NADH (mM) on the enzyme's action on L-tyrosine are depicted in [Monophenol] ss = R. 24,25) When the dopachrome accumulation was measured ( Fig. 2A inset, recordings a-d), the lag period diminished for lower concentration ( Fig.…”

Section: Monophenolase Activitymentioning

confidence: 99%

Melanogenesis Inhibition Due to NADH

García‐Molina¹,

Muñoz‐Muñoz²,

Garcia-Molina³

et al. 2010

Bioscience, Biotechnology, and Biochemistry

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The effect of NADH on melanogenesis under aerobic conditions involves three types of reaction: (a) acting as tyrosinase substrate (a competitive substrate of Ltyrosine and L-DOPA), (b) irreversible inactivation acting as a suicide substrate of tyrosinase, and (c) nonenzymatic reduction of o-dopaquinone by NADH. Under anaerobic conditions, NADH irreversibly inhibits the enzymatic forms met-tyrosinase and deoxy-tyrosinase. In this paper, we kinetically characterize this coenzyme as it acts as a tyrosinase suicide substrate and propose a kinetic mechanism to explain its oxidation by tyrosinase. In addition, the compound is characterized as an irreversible inhibitor of met-tyrosinase and deoxytyrosinase.

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“…16,17) Briefly, cells were washed with PBS and then lysed by incubation at 4°C for 30 min in lysis buffer (10 mm Tris-HCl containing 150 mm NaCl, 2 mm EGTA, 2 mm dithiothreitol, 1 mm sodium orthovanadate, 1 mm phenylmethylsulfonyl fluoride, 10 µg/mL leupeptin, and 10 µg/ mL aprotinin). After incubation, the cell lysates were centrifuged at 12000×g for 10 min to obtain the supernatant as the enzyme source.…”

Section: Determination Of Melanin Contentmentioning

confidence: 99%

Cyclohexanediol Bis-Ethylhexanoate Inhibits Melanogenesis of Murine B16 Melanoma and UV-Induced Pigmentation in Human Skin

Lim¹,

Kim²,

Yoo³

et al. 2013

Biological & Pharmaceutical Bulletin

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The role of cyclohexane diester analogues in the formation of melanin has been recently reported. In the present study, we investigated the inhibitory effect of cyclohexanediol bis-ethylhexanoate (CHEH) on melanogenesis in B16 melanoma cells and on UV-B-induced pigmentation in human skin. CHEH significantly reduced the melanin content in a dose-dependent manner, without cytotoxic effects at the effective concentrations. Moreover, CHEH dose-dependently inhibited tyrosinase activity in B16 melanoma cells, as confirmed by Western blot analysis of the tyrosinase protein levels. However, tyrosinase transcript levels remained unchanged under the same experimental conditions. These results indicate that CHEH inhibited melanogenesis in B16 melanoma cells by regulating tyrosinase activity at the post-transcriptional level. On the other hand, in a cell-free system, CHEH did not inhibit tyrosinase activity. This indicated that CHEH suppressed the pigmentation of melanocytes by indirectly regulating tyrosinase activity. Finally, in a clinical trial, a cream containing 1.0% CHEH showed good whitening effect on UV-induced pigmented human skin without adverse effects. In conclusion, we suggest that CHEH may be an effective inhibitor of melanogenesis and useful effects in the treatment of hyperpigmented disorders.Key words anti-melanogenesis; cyclohexanediol bis-ethylhexanoate; tyrosinase; whitening Melanogenesis is the process by which melanin-the dark pigment in melanocytes-is synthesized. Melanin determines skin color and protects the skin against UV light. However, abnormal accumulation of melanin results in hyperpigmentary disorders, such as freckles, skin discoloration, and pigmented age spots, which represent serious challenges in dermatology and beauty care.

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Tyrosinase: kinetic analysis of the transient phase and the steady state

Cited by 106 publications

References 25 publications

Effect of tetrahydropteridines on the monophenolase and diphenolase activities of tyrosinase

Effect of tetrahydropteridines on the monophenolase and diphenolase activities of tyrosinase

Melanogenesis Inhibition Due to NADH

Cyclohexanediol Bis-Ethylhexanoate Inhibits Melanogenesis of Murine B16 Melanoma and UV-Induced Pigmentation in Human Skin

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