Catecholase Activity Of Tyrosinase Research Articles

Study of Novel Furocoumarin Derivatives on Anti-Vitiligo Activity, Molecular Docking and Mechanism of Action.

Vitiligo is a common chronic dermatological abnormality that afflicts tens of millions of people. Furocoumarins isolated from Uygur traditional medicinal material Psoralen corylifolia L. have been proven to be highly effective for the treatment of vitiligo. Although many furocoumarin derivatives with anti-vitiligo activity have been synthesized, their targets with respect to the disease are still ambiguous. Fortunately, the JAKs were identified as potential targets for the disease and its inhibitors have been proved to be effective in the treatment of vitiligo in many clinical trials. Thus, sixty-five benzene sulfonate and benzoate derivatives of furocoumarins (7a–7ad, 8a–8ag) with superior anti-vitiligo activity targeting JAKs were designed and synthesized based on preliminary research. The SAR was characterized after the anti-vitiligo-activity evaluation in B16 cells. Twenty-two derivatives showed more potent effects on melanin synthesis in B16 cells than the positive control (8-MOP). Among them, compounds 7y and 8 not only could increase melanin content, but they also improved the catecholase activity of tyrosinase in a concentration-dependent manner. The docking studies indicated that they were able to interact with amino acid residues in JAK1 and JAK2 via hydrogen bonds. Furthermore, candidate 8 showed a moderate inhibition of CXCL−10, which plays an important role in JAK–STAT signaling. The RT-PCR and Western blotting analyses illustrated that compounds 7y and 8 promoted melanogenesis by activating the p38 MAPK and Akt/GSK-3β/β-catenin pathways, as well as increasing the expressions of the MITF and tyrosinase-family genes. Finally, furocoumarin derivative 8 was recognized as a promising candidate for the fight against the disease and worthy of further research in vivo.

Using tyrosinase as a monophenol monooxygenase: A combined strategy for effective inhibition of melanin formation.

Tyrosinase is a binuclear copper-containing metalloprotein that leads the fast and regio-selective o-hydroxylation of monophenols to o-diphenols. However, the subsequent second oxidation to produce o-quinones, i.e., melanin precursors, from the o-diphenols has restricted its use to the production of functional o-diphenol derivatives. Herein, we present a combined strategy for the effective inhibition of melanin formation in tyrosinase reaction, which allows the use of tyrosinase as a monophenol monooxygenase. The o-diphenolic products were protected from being oxidized in the tyrosinase reaction by borate ions and L-ascorbic acid (LAA). Borate-o-diphenol complexes were favorable formed at high pH and consequentially protected the o-diphenolic products from the catecholase activity of tyrosinase. LAA not only directly reduced the byproduct, o-quinones, into o-diphenols but also assisted the completion of the tyrosinase reaction cycle by removing a hydroxyl group attached to the copper metal cluster at the active site of the met-form tyrosinase. The regio-selective o-hydroxylation of 7,4'-dihydroxyisoflavone (daidzein) to produce 7,3',4'-trihydroxyisoflavone (3'-ODI) was successfully carried out by whole E. coli cell biotransformation with heterologously expressed tyrosinase from Bacillus megaterium. The yield of this o-hydroxylation of 5 mM daidzein in one-pot 400 mL reaction was ca. 100% in 90 min and the productivity was 16.3 mg 3'-ODI · L(-1) · h(-1) · DCW mg(-1), which is considerably higher than that of other monooxygenases. The method effectively abolished melanin synthesis, so that the o-diphenolic product remained stable without enzyme inactivation. Other monophenolic phytochemicals such as resveratrol and genistein could be subjected to the same strategy. After 1 h, 1 mM of genistein and resveratrol were both converted to orobol and piceatannol, respectively, with ca. 95% conversion yield. These results support the strong potential of tyrosinase as a monooxygenase for regio-selective o-hydroxylation of various monophenolic compounds.

Exploring the interaction of N/S compounds with a dicopper center: tyrosinase inhibition and model studies.

Tyrosinase (Ty) is a copper-containing enzyme widely present in plants, bacteria, and humans, where it is involved in biosynthesis of melanin-type pigments. Development of Ty inhibitors is an important approach to control the production and the accumulation of pigments in living systems. In this paper, we focused our interest in phenylthiourea (PTU) and phenylmethylene thiosemicarbazone (PTSC) recognized as inhibitors of tyrosinase by combining enzymatic studies and coordination chemistry methods. Both are efficient inhibitors of mushroom tyrosinase and they can be considered mainly as competitive inhibitors. Computational studies verify that PTSC and PTU inhibitors interact with the metal center of the active site. The KIC value of 0.93 μM confirms that PTSC is a much more efficient inhibitor than PTU, for which a KIC value of 58 μM was determined. The estimation of the binding free energies inhibitors/Ty confirms the high inhibitor efficiency of PTSC. Binding studies of PTSC along with PTU to a dinuclear copper(II) complex ([Cu2(μ-BPMP)(μ-OH)](ClO4)2 (1); H-BPMP = 2,6-bis-[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) known to be a structural and functional model for the tyrosinase catecholase activity, have been performed. Interactions of the compounds with the dicopper model complex 1 were followed by spectrophotometry and electrospray ionization (ESI). The molecular structure of 1-PTSC and 1-PTU adducts were determined by single-crystal X-ray diffraction analysis showing for both an unusual bridging binding mode on the dicopper center. These results reflect their adaptable binding mode in relation to the geometry and chelate size of the dicopper center.

Inhibitory Effect of Hydroxyindoles and their Analogues on Human Melanoma Tyrosinase

A recent study showed that N-acylserotonin derivatives have strong inhibitory activity against tyrosinase. To clarify the role of the 5-hydroxy group in the indole ring, 2-, 4-, 5-, 6-, and 7-hydroxyindole and 11 related compounds such as 5-hydroxyindan and 6-hydroxyquinoline were tested for their inhibition of catecholase activity of tyrosinase from human HMV-II melanoma cells. 6-Hydroxyindole (5) and 7-hydroxyindole (6) were potent inhibitors, while 5-hydroxyindole (4) was a weaker inhibitor than the above-mentioned compounds (IC50 = 20, 79, 366, and 342 microM for 5, 6, 4, and kojic acid, respectively). 2-Hydroxycarbazole was also active (IC50 = 190 microM), 5-hydroxyindan, 4-aminophenol, and harmalol were slightly active, and other compounds were inactive as an inhibitor. A similar pattern of inhibition was found with these compounds against mouse B16 melanoma tyrosinase, but with some differences from that for HMV-II tyrosinase. Kinetic analysis with HMV-II tyrosinase showed that the inhibition by hydroxyindoles 4, 5, and 6 was competitive with respect to the substrate L-DOPA. Melanin formation in HMV-II cells was suppressed by 14% with 10 microM 5 without cytotoxicity, but 30 or 100 microM 5 decreased the cell viability. The present results suggest that 6-hydroxyindole is a potential and useful pharmacophore of antimelanogenic agents and that the position of a phenolic hydroxy group in a specific heterocyclic ring such as in indole is possibly optimized to yield more active inhibitors for tyrosinase.

Binding of 2-Hydroxypyridine-N-oxide on Dicopper(II) Centers: Insights into Tyrosinase Inhibition Mechanism by Transition-State Analogs

2-Hydroxypyridine-N-oxide (HOPNO) is described as a new and efficient transition-state analog (TS-analog) inhibitor for the mushroom tyrosinase with an IC(50) = 1.16 microM and a K(I) = 1.8 microM. Using the binuclear copper(II) complex [Cu(2)(BPMP)(mu-OH)](ClO(4))(2) (2) known as a functional model for the tyrosinase catecholase activity, we isolated and fully characterized a 1:1 (2)/OPNO adduct in which the HOPNO is deprotonated and chelates only one Cu-atom of the binuclear site in a bidentate mode. On the basis of these results, a structural model for the tyrosinase inhibition by HOPNO is proposed.

Dimethyl Sulfide, a Volatile Flavor Constituent, Is a Slow-Binding Inhibitor of Tyrosinase

In this paper, the inhibition of tyrosinase by a volatile compound is kinetically analyzed for the first time. The results obtained show that the volatile flavor constituent dimethyl sulfide (DMS) inhibits the catecholase activity of tyrosinase in a nonclassical manner. A decrease in the initial velocity to a inhibited steady-state velocity can be observed within a few minutes. This time dependence, which is unaltered by prior incubation of the enzyme with the inhibitor, is consistent with a first-order transition. Both the initial and the constant rates decreased with increasing concentrations of inhibitor. The kinetic data obtained correspond to those for a postulated mechanism involving rapid formation of an enzyme–inhibitor complex that subsequently undergoes a relatively slow reversible reaction. These results, together with the high levels of DMS precursor in certain organisms, suggest a physiological role for this compound within plant tissues.

4-Substituted Resorcinols (Sulfite Alternatives) as Slow-Binding Inhibitors of Tyrosinase Catecholase Activity

A kinetic study of the inhibition of mushroom tyrosinase catecholase activity by 4-substituted resorcinols has been made. The results obtained show that 4-substituted resorcinols inhibit tyrosinase in a nonclassical manner and that the inhibition is characterized by a long transient phase. Progress curves of enzymatic reaction in the presence of inhibitor show a progressive decrease in initial velocity followed by a constant steady-state rate. Both the initial and the constant rates decreased with increasing concentrations of inhibitor. Kinetic data obtained correspond to those for a postulated mechanism involving rapid formation of an enzyme−inhibitor complex that subsequently undergoes a relatively slow reversible reaction. The kinetic parameters characterizing this time-dependent inhibition were evaluated by means of nonlinear regression of the product accumulation curves. Keywords: Tyrosinase; 4-hexylresorcinol; slow-binding inhibitors

Kojic acid, a cosmetic skin whitening agent, is a slow-binding inhibitor of catecholase activity of tyrosinase.

It was found that kojic acid, which is used in cosmetics for its excellent whitening effect, inhibits catecholase activity of tyrosinase in a non-classical manner. A decrease in the initial velocity to a steady-state inhibited velocity can be observed over a few minutes. This time-dependence, which is unaltered by prior incubation of the enzyme with the inhibitor, is consistent with a first-order transition. The kinetic data obtained correspond to those for a postulated mechanism that involves the rapid formation of an enzyme inhibitor complex that subsequently undergoes a relatively slow reversible reaction. Kinetic parameters characterizing this type of inhibition were evaluated by means of nonlinear regression of product accumulation curves.

Binuclear copper complex model of tyrosinase

The synthesis is reported of a binuclear copper(I) complex 2 which exhibits the catalytic phenolase and catecholase activity of tyrosinase.

An improvement of the spectrophotometric method for the determination of tyrosinase catecholase activity by Besthorn's hydrazone

A method for the determination of the catecholase activity of tyrosinase (monophenol mono-oxygenase, EC 1.14.18.1) was described in an earlier paper by Pifferi and Baldassari (1). This method is based on the condensation of Besthorn's hydrazone with the quinone obtained by enzymatic oxidation of pyrocatechol, the subsequent extraction of the reaction's condensation compound with CHCl 3, and lastly, the spectrophotometric reading at 500 nm of the chloroformic phase. This method is suitable for the determination of tyrosinase catecholase activity in both solutions and suspensions. The proposed improvement of the above method consists of dissolving the condensation product in the reaction environment with an opportune solvent, rather than extracting it with CHCl 3. The advantages obtained are the more rapid and easier test performance and the higher sensitivity of the method. This is due to the lower final reaction volume (6 ml) as compared to the volume of the extracted chloroformic phase (25 ml) with the original method. When the improved method is applied to enzymatic preparations in solution, there is no difficulty with the spectrophotometric reading; in the case of suspensions, the reaction mixture can be read after decantation, or, better, after filtration without suction through a filter crucible with a porous septum.

A spectrophotometric method for the determination of the catecholase activity of tyrosinase by Besthorn's hydrazone

A quick and easily reproducible procedure for determining the catecholase activity of tyrosinase is described. The o-benzoquinone formed during the oxidation of catechol is condensed with Besthorn's hydrazone. The absorbance of the condensation compound, extracted with chloroform, is read at 500 nm.

On the activity of tyrosinase in tobacco seeds

Water or buffered extracts from tobacco seeds (Mont Calme brun) showed both cresolase and catecholase activity of tyrosinase, which was inhibited by 10−2 M thiourea. No difference of activity could be observed in extracts from old and fresh seeds. Unexpectedly, chlorogenic acid is not oxidized by this tyrosinase.

A Spectrophotometric Method for the Determination of the Catecholase Activity of Tyrosinase and Some of its Applications1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Spectrophotometric Method for the Determination of the Catecholase Activity of Tyrosinase and Some of its Applications1Mohamed Ashraf El-Bayoumi and Earl FriedenCite this: J. Am. Chem. Soc. 1957, 79, 18, 4854–4858Publication Date (Print):September 1, 1957Publication History Published online1 May 2002Published inissue 1 September 1957https://doi.org/10.1021/ja01575a009RIGHTS & PERMISSIONSArticle Views659Altmetric-Citations47LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (549 KB) Get e-Alerts Get e-Alerts

A New Method for the Measurement of Tyrosinase Catecholase Activity. II. Catecholase Activity Based on the Initial Reaction Velocity

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Method for the Measurement of Tyrosinase Catecholase Activity. II. Catecholase Activity Based on the Initial Reaction VelocityWilbur H. Miller, M. Frank Mallette, Lloyd J. Roth, and Charles R. DawsonCite this: J. Am. Chem. Soc. 1944, 66, 4, 514–519Publication Date (Print):April 1, 1944Publication History Published online1 May 2002Published inissue 1 April 1944https://doi.org/10.1021/ja01232a004RIGHTS & PERMISSIONSArticle Views338Altmetric-Citations58LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (716 KB) Get e-Alerts Get e-Alerts

A New Method for the Measurement of Tyrosinase Catecholase Activity

A New Method for the Measurement of Tyrosinase Catecholase Activity