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del Mar Garcia-Molina M, Muñoz-Muñoz JL, Berna J, García-Ruiz PA, Rodriguez-Lopez JN, Garcia-Canovas F. Catalysis and inactivation of tyrosinase in its action on hydroxyhydroquinone. IUBMB Life 2014; 66:122-7. [PMID: 24578277 DOI: 10.1002/iub.1250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/28/2014] [Accepted: 01/31/2014] [Indexed: 11/07/2022]
Abstract
Hydroxyhydroquinone (HHQ) was characterized kinetically as a tyrosinase substrate. A kinetic mechanism is proposed, in which HHQ is considered as a monophenol or as an o-diphenol, depending on the part of the molecule that interacts with the enzyme. The kinetic parameters obtained from an analysis of the measurements of the initial steady state rate of 2-hydroxy p-benzoquinone formation were kcatapp=229.0±7.7 s(-1) and KMapp,HHQ=0.40±0.05 mM. Furthermore, the action of tyrosinase on HHQ led to the enzyme's inactivation through a suicide inactivation mechanism. This suicide inactivation process was characterized kinetically by λmaxapp (the apparent maximum inactivation constant) and r, the number of turnovers made by 1 mol of enzyme before being inactivated. The values of λmaxapp and r were (8.2±0.1)×10(-3) s(-1) and 35,740±2,548, respectively.
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Affiliation(s)
- Maria del Mar Garcia-Molina
- GENZ: Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Campus de Excelencia Internacional "Mare Nostrum", Universidad de Murcia, Espinardo, Murcia, E-30100, Spain
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2
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Manivasagan P, Venkatesan J, Sivakumar K, Kim SK. Actinobacterial melanins: current status and perspective for the future. World J Microbiol Biotechnol 2013; 29:1737-50. [PMID: 23595596 DOI: 10.1007/s11274-013-1352-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 04/11/2013] [Indexed: 01/18/2023]
Abstract
Melanins are enigmatic pigments that are produced by a wide variety of microorganisms including several species of bacteria and fungi. Melanins are biological macromolecules with multiple important functions, yet their structures are not well understood. Melanins are frequently used in medicine, pharmacology, and cosmetics preparations. Melanins also have great application potential in agriculture industry. They have several biological functions including photoprotection, thermoregulation, action as free radical sinks, cation chelators, and antibiotics. Plants and insects incorporate melanins as cell wall and cuticle strengtheners, respectively. Actinobacteria are the most economically as well as biotechnologically valuable prokaryotes. However, the melanin properties are, in general, poorly understood. In this review an evaluation is made on the present state of research on actinobacterial melanins and its perspectives. The highlights include the production and biotechnological applications of melanins in agriculture, food, cosmetic and medicinal fields. With increasing advancement in science and technology, there would be greater demands in the future for melanins produced by actinobacteria from various sources.
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Affiliation(s)
- Panchanathan Manivasagan
- Marine Biotechnology Laboratory, Department of Chemistry and Marine Bioprocess Research Center, Pukyong National University, Busan, 608-737, Republic of Korea,
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3
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Abstract
Melanins are the principal surface pigments in vertebrates and, in humans, play a major role in photoprotection. Although the product (melanin) has a mainly protective function in the skin, the process of melanogenesis represents a potential cellular hazard and is confined to special membrane-limited organelles (melanosomes) in a set of specialized dendritic cells (melanocytes) which synthesize the pigment and transfer it to recipient cells. Malignant melanocytes tend to exhibit up-regulated melanogenesis and defective melanosomes. These features suggest ways in which anti-melanoma therapy may be specifically targeted. Two general chemotherapeutic modalities are considered: 1 The 'Achilles heel' approach in which the generation of reactive quinones capable of leaking into the cytosolic compartment and causing structural and functional derangement is encouraged by the use of analogue substrates. 2 The 'Trojan horse' approach, in which a cytotoxic agent is selectively released by a tyrosinase-dependent mechanism.
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4
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Kostrzewa RM, Brus R. Destruction of catecholamine-containing neurons by 6-hydroxydopa, an endogenous amine oxidase cofactor. Amino Acids 1999; 14:175-9. [PMID: 9871458 DOI: 10.1007/bf01345259] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The amino acid, 6-hydroxydopa (6-OHDOPA), found at the active site of amine oxidases, exists as a keto-enol. Exogenously administered 6-OHDOPA is an excitotoxin like beta-N-oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA), acting at the non-N-methyl-D-aspartate (non-NMDA) alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor. BMAA and BOAA are causal factors of neurolathyrism in humans. Much exogenously administered 6-OHDOPA is biotransformed by aminoacid decarboxylase (AADC) to the highly potent and catecholamine-(CA) selective neurotoxin, 6-hydroxydopamine (6-OHDA). 6-OHDOPA destroys locus coeruleus noradrenergic perikarya and produces associated denervation of brain by norepinephrine-(NE) containing fibers. Opiopeptides and opioids enhance neurotoxic effects of 6-OHDOPA on noradrenergic nerves, by a naloxone-reversible process. An understanding of mechanisms underlying neurotoxic effects of 6-OHDOPA can be helpful in defining actions of known and newfound amino acids and for investigating their potential neurotoxic properties.
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Affiliation(s)
- R M Kostrzewa
- Department of Pharmacology, Quillen College of Medicine, East Tennessee State University, Johnson City, USA
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Salinas C, García-Borrón JC, Solano F, Lozano JA. Dopachrome tautomerase decreases the binding of indolic melanogenesis intermediates to proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1204:53-60. [PMID: 8305475 DOI: 10.1016/0167-4838(94)90032-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dopachrome tautomerase (DCT) is a recently characterized enzyme contributing to the control of melanogenesis in mammals. The enzyme catalyzes the rearrangement of L-Dopachrome (L-DC) to 5,6-dihydroxyindole 2-carboxylic acid (DHICA), while the spontaneous rearrangement of L-DC leads to 5,6-dihydroxyindole (DHI). Due to the lower reactivity of DHICA in comparison to DHI, DCT could provide a protective mechanism against the cytotoxicity of decarboxylated indolic melanogenic intermediates by limiting the formation of these highly reactive decarboxylated species within melanocytes. We have followed the binding of radioactive melanogenic precursors to a model protein, bovine serum albumin (BSA). Using L-DC as initial melanin precursor, this binding was decreased by DCT in a concentration-dependent manner. In the presence of tyrosinase, the binding of L-Dopa-derived intermediates to BSA was also decreased by DCT and the percentage of decrease was even higher than using L-DC as initial melanin precursor. SDS-PAGE followed by fluorographic detection of radioactive bands showed the formation of covalent adducts between BSA and melanin precursors, as well as of aggregated forms of this protein. This aggregation was also diminished by DCT. These data indicate that DCT could play a protective role against the cytotoxic action of decarboxylated indoles within mammalian melanocytes.
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Affiliation(s)
- C Salinas
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, Spain
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Rodriguez-López JN, Varón R, García-Cánovas F. Oxidation of 6-hydroxydopamine catalyzed by tyrosinase. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1993; 25:1175-82. [PMID: 8405659 DOI: 10.1016/0020-711x(93)90596-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
1. The oxidation of 3,4-dihydroxyphenylethylamine (dopamine) by O2 catalyzed by tyrosinase yields 4-(2-aminoethyl)-1,2-benzoquinone, with its amino group protonated (o-dopaminequinone-H+), which evolves non-enzymatically through two branches or sequences of reactions, whose respective operations are determined by the pH of the medium. 2. The cyclization branch of o-dopaminequinone-H+ takes place in the entire range of pH and is the only significant branch at pH > or = 6. 3. The hydroxylation branch of o-dopaminequinone-H+ only operates significantly at pH < 6, and involves the accumulation of 2,4,5-trihydroxyphenylethylamine (6-hydroxydopamine), identified by high performance liquid chromatography (HPLC). 4. 6-hydroxydopamine is also a substrate of tyrosinase. The identification and evolution of the oxidation products of 6-hydroxydopamine has been carried out by spectrophotometry and HPLC assays.
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Rodríguez-López JN, Bañón-Arnao M, Martinez-Ortiz F, Tudela J, Acosta M, Varón R, García-Cánovas F. Catalytic oxidation of 2,4,5-trihydroxyphenylalanine by tyrosinase: identification and evolution of intermediates. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1160:221-8. [PMID: 1445949 DOI: 10.1016/0167-4838(92)90011-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The oxidation of 3,4-dihydroxyphenylalanine (dopa) by O2 catalyzed by tyrosinase yields 4-(2-carboxy-2-aminoethyl)-1,2-benzoquinone, with its amino group protonated (o-dopaquinone-H+). This evolves non-enzymatically through two branches (cyclization and/or hydroxylation), whose respective operations are determined by pH. The hydroxylation branch of o-dopaquinone-H+ only operates significantly at pH < or = 5.0 and involves the accumulation of 2,4,5-trihydroxyphenylalanine (topa), which has been detected by high-performance liquid chromatography (HPLC). This last compound is also a substrate of tyrosinase. The oxidation of topa by both tyrosinase and periodate yields 5-(2-carboxy-2-aminoethyl)-4-hydroxy-1,2-benzoquinone, with its amino group protonated (o-topaquinone-H+), which is red (RTQH) (lambda max 272-485 nm) at pH 7.0 and yellow (TTQH) (lambda max 265-390 nm) at pH 3.0. This is based on pKa 4.5 of the 2-OH group of the benzene ring of o-topaquinone-H+, as derived from spectrophotometric and HPLC assays. At physiological pH, RTQH undergoes deprotonation of the ammonium group of the side chain to yields RTQ, which cyclize into 2-carboxy-2,3-dihydroxyindolen-5,6-quinone (dopachrome), with a 1:1 stoichiometry and first-order kinetics. The evolution of RTQH has been analyzed by spectrophotometry, HPLC, cyclic voltammetry and constant potential electrolytic assays. From HPLC assays, the value of the first-order constant for the evolution of RTQH at pH 7.0 (kRTQHapp 4.83 x 10(-5) s-1), as well as of the rate constant for the cyclization step of RTQ (kRTQc 2.53 x 10(-3) s-1) were determined.
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Affiliation(s)
- J N Rodríguez-López
- Departamento de Química-Física, E.U. Politécnica de Albacete, Universidad de Castilla-La Mancha, Spain
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García-Moreno M, Rodríguez-López JN, Martínez-Ortiz F, Tudela J, Varón R, García-Cánovas F. Effect of pH on the oxidation pathway of dopamine catalyzed by tyrosinase. Arch Biochem Biophys 1991; 288:427-34. [PMID: 1910309 DOI: 10.1016/0003-9861(91)90216-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The oxidation of 3,4-dihydroxyphenylethylamine (dopamine) by O2 catalyzed by tyrosinase yields 4-(2-aminoethyl)-1, 2-benzoquinone (o-dopaminequinone), which evolves nonenzymatically through two branches or sequences of reactions, whose respective operations are determined by the pH of the medium. The cyclization branch of o-dopaminequinone takes place in the entire range of pH and is the only significant branch at pH greater than or equal to 6. The hydroxylation branch of o-dopaminequinone only operates significantly at pH less than 6, and involves the accumulation of 2,4,5-trihydroxyphenylethylamine (6-hydroxydopamine) and 5-(2-aminoethyl)-2-hydroxy-1,4-benzoquinone (p-topaminequinone), identified from cyclic voltammetry assays. The kinetic characterization of the hydroxylation branch of o-dopaminequinone has been carried out by spectrophotometric and oxymetric assays. The successful fitting of data to the kinetic behavior predicted by the kinetic analysis at both pH greater than or equal to 6 and pH less than 6 confirms the overall oxidation pathway proposed for the dopamine oxidation catalyzed by tyrosinase. The antitumoral power of dopamine is possibly enhanced by the high cytotoxicity of 6-hydroxydopamine and p-topaminequinone, accumulated at the acidic pH characteristic of melanosomes and melanome cells.
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Affiliation(s)
- M García-Moreno
- Cátedra de Química-Física, E. U. Politécnica, Universidad de Castilla-La Mancha, Albacete, Spain
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9
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Rodríguez-López JN, Tudela J, Varón R, García-Cánovas F. Kinetic study on the effect of pH on the melanin biosynthesis pathway. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1076:379-86. [PMID: 1900435 DOI: 10.1016/0167-4838(91)90480-n] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This paper deals with the quantitative description of the regulatory effect of pH on the oxidation pathway of L-dopa to yield melanins. Tyrosinase catalyzes the oxidation by molecular oxygen of L-dopa to o-dopaquinone, which evolves non-enzymatically through a branched pathway with cyclization or hydroxylation reactions. The production of several quinones and semiquinones in the pathway has also been reported. The intermediates of the hydroxylation branch have been identified and the corresponding rate constants have been determined. These compounds, such as have been detected in melanosomes and in tumoral cells, have great cytotoxic power and could have physiological significance in acidic media.
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Affiliation(s)
- J N Rodríguez-López
- Cátedra de Química Industrial, Universidad de Castilla-La Mancha, Albacete, Spain
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Thody AJ, Oliver I, Sherbet GV. Cytotoxicity of 4-hydroxyanisole and tyrosinase activity in variant cell lines of B16 melanoma. EUROPEAN JOURNAL OF CANCER & CLINICAL ONCOLOGY 1988; 24:1879-84. [PMID: 2851444 DOI: 10.1016/0277-5379(88)90101-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The melanocytotoxic effects of 4-hydroxyanisole (4-OHA) are thought to depend upon its conversion to toxic oxidation products by the enzyme tyrosinase. In this study, the cytotoxicity of 4-OHA was examined in different B16 melanoma cell lines that show varying levels of tyrosinase and after stimulation by melanocyte-stimulating hormone (MSH) and all-trans-retinoic acid (RA). 4-OHA decreased cell survival of three melanotic and one amelanotic cell line in culture, but the effect was unrelated to their tyrosinase activity or the subcellular localization of the enzyme. Although stimulation of tyrosinase activity with RA enhanced the cytotoxicity of 4-OHA, no similar enhancement occurred with alpha-MSH. It appears that there is no relationship between the cytotoxic effects of 4-OHA and intracellular tyrosinase and the enhancement of its cytotoxicity by RA may well be related to the antiproliferative effects of the retinoid.
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Affiliation(s)
- A J Thody
- Department of Dermatology, University of Newcastle upon Tyne, U.K
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Kalyanaraman B, Korytowski W, Pilas B, Sarna T, Land EJ, Truscott TG. Reaction between ortho-semiquinones and oxygen: pulse radiolysis, electron spin resonance, and oxygen uptake studies. Arch Biochem Biophys 1988; 266:277-84. [PMID: 2845864 DOI: 10.1016/0003-9861(88)90259-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The cytotoxicity to tumor cells or cardiotoxic side effects of certain para-quinone antitumor drugs have been attributed to the corresponding semiquinones and derived superoxide and hydroxyl radicals. It has also been suggested that ortho-semiquinones, including those that arise during melanogenesis, produced via either the one-electron oxidation of catechol(amine)s or the one-electron reduction of the corresponding quinones, react with molecular oxygen to give superoxide and hydrogen peroxide. Furthermore it has been shown that catechol(amine)s which form noncyclizable quinones are more cytotoxic toward melanogenic cells than those forming cyclizable quinones. In order to provide further kinetic information on the interaction of oxygen with ortho-semiquinones, using pulse radiolysis we directly measured the rates of reaction of various ortho-semiquinones with molecular oxygen. The semiquinones of the corresponding catechol(amine)s were also produced by the horseradish peroxidase/hydrogen peroxide system, and detected by electron spin resonance spectroscopy using the spin stabilization method. Oxygen consumption was monitored using a standard Clark oxygen electrode. Our data indicate that while ortho-semiquinones from catechol(amine)s and catechol estrogens do not react with molecular oxygen at a rate equal to or greater than k less than or equal to 10(5) M-1 s-1, semiquinones from hydroxy-substituted catechol(amine)s react with dioxygen with rates in the range k = 10(6)-10(7) M-1 s-1.
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Affiliation(s)
- B Kalyanaraman
- Department of Radiology, Medical College of Wisconsin, Milwaukee 53226
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Nakamura T, Seki S, Matsubara O, Ito S, Kasuga T. Specific incorporation of 4-S-cysteinylphenol into human melanoma cells. J Invest Dermatol 1988; 90:725-8. [PMID: 3361142 DOI: 10.1111/1523-1747.ep12560926] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The incorporation of 4-S-cysteinylphenol (4-S-CP), a tyrosine analog, into malignant melanoma cells was evaluated. 4-S-CP was specifically incorporated into the melanotic melanoma cells (HMV-II), which have activity for melanin synthesis, but was scarcely incorporated into HeLA S3 or HMV-I cells, which have no activity for melanin synthesis. Electron microscopic autoradiography revealed that the intracellular localization of 4-S-CP was closely correlated with melanogenesis and that 4-S-CP served as an initial substrate for tyrosinase and was utilized in melanin synthesis. On the basis of these findings we hypothesize that tyrosinase is required for intracellular incorporation of 4-S-CP. This specific incorporation of 4-S-CP into melanoma cells should be useful in the development of an effective procedure for chemotherapy of malignant melanomas and in analysis of melanin synthesis.
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Affiliation(s)
- T Nakamura
- Second Department of Pathology, School of Medicine, Tokyo Medical and Dental University, Japan
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Korytowski W, Sarna T, Kalyanaraman B, Sealy RC. Tyrosinase-catalyzed oxidation of dopa and related catechol(amine)s: a kinetic electron spin resonance investigation using spin-stabilization and spin label oximetry. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 924:383-92. [PMID: 3036239 DOI: 10.1016/0304-4165(87)90152-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The oxidation of four catechol(amine)s by tyrosinase has been studied by electron spin resonance and optical methods. Rates of oxygen consumption and of dopaquinone and dopachrome formation during the oxidation of dopa have been measured, and compared with rates of dopasemiquinone production measured using spin-stabilization procedures. In the presence of spin-stabilizing metal ions, production of semiquinone is approximately quantitative. Time-dependent ESR spectra obtained from dopa and dopamine show a slow regeneration of semiquinone, suggesting that a semiquinone precursor is slowly reformed. In contrast, time-dependent spectra for 4-methylcatechol and N-acetyldopamine show decay of the primary semiquinone together with buildup of a secondary semiquinone apparently derived from the corresponding 6-hydroxy-catechol(amine). Thus, catecholamines that give rise to a cyclizable quinone show a pattern of behavior that differs from those that produce a non-cyclizable quinone. These results are discussed in terms of their possible significance to melanogenesis and the toxicity of catechol(amine)s, which has been attributed to production of semiquinones and/or other oxygen radicals.
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Yamada I, Seki S, Matsubara O, Ito S, Suzuki S, Kasuga T. The cytotoxicity of cysteinylcatechols and related compounds to human melanoma cells in vitro. J Invest Dermatol 1987; 88:538-40. [PMID: 3572026 DOI: 10.1111/1523-1747.ep12470098] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
L-3,4-Dihydroxyphenylalanine (L-dopa) and its structural analogs are known to be potently cytotoxic to melanoma cells. We examined the effects of cysteinylcatechols and related compounds, which were newly synthesized as cysteinyl derivatives of L-dopa, on the growth of human melanoma cells in vitro, and their actions were compared with those of L-dopa. 4-S- and 3-S-Cysteinylcatechols showed significantly more potent cytotoxicity to melanoma cells than did L-dopa, and 2-S-cysteinylhydroquinone was next to the catechols in potency. The mechanism of action may involve interaction with the melanocyte-specific enzyme, tyrosinase, for which the cysteinylcatechols could become a better substrate than L-dopa itself. 4-S-Cysteaminylphenol was almost comparable to L-dopa in cytotoxicity, suggesting that this phenol might be oxidized to the corresponding catechol by tyrosinase within the melanoma cells.
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15
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Morrison ME, Yagi MJ, Cohen G. In vitro studies of 2,4-dihydroxyphenylalanine, a prodrug targeted against malignant melanoma cells. Proc Natl Acad Sci U S A 1985; 82:2960-4. [PMID: 3921968 PMCID: PMC397686 DOI: 10.1073/pnas.82.9.2960] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We have evaluated the chemotherapeutic potential of 2,4-dihydroxyphenylalanine, a targeted prodrug that can be hydroxylated by tyrosinase (monophenol monooxygenase, EC 1.14.18.1) within melanoma cells to form the cellular toxin 2,4,5-trihydroxyphenylalanine (6-hydroxydopa). 2,4-Dihydroxyphenylalanine proved to be cytotoxic to both B-16 and Cloudman melanoma cells in vitro. The immediate effects of 2,4-dihydroxyphenylalanine included inhibition of DNA, RNA, and protein syntheses. In contrast, no decrease in macromolecular synthesis or viability was seen against cultures of MJY-alpha mammary tumor or L-1210 leukemia, two cell types that do not contain tyrosinase. Within the melanoma cultures, greater cytotoxicity was seen against melanotic (tyrosinase-containing) cells than against amelanotic (tyrosinase-lacking) cells. The cytotoxicity of 2,4-dihydroxyphenylalanine was blocked by 1-phenylthiourea, an inhibitor of tyrosinase. These results show that 2,4-dihydroxyphenylalanine is toxic to melanoma cells and that activation of 2,4-dihydroxyphenylalanine requires the presence of tyrosinase.
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Van Rens GH, De Jong PT, Demols EE, Brihaye-Van Geertruyden MF. Uveal malignant melanoma and levodopa therapy in Parkinson's disease. Ophthalmology 1982; 89:1464-6. [PMID: 7162789 DOI: 10.1016/s0161-6420(82)34616-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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17
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Wick MM, Rosowsky A, Ratliff J. Antitumor effects of L-glutamic acid dihydroxyanilides against experimental melanoma. J Invest Dermatol 1980; 74:112-4. [PMID: 6766171 DOI: 10.1111/1523-1747.ep12520030] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
L-glutamic acid, gamma-(p-hydroxyanilide), is a naturally occurring metabolic inhibitor found in mushrooms and shown to be active against B-16 melanoma in vivo. We have prepared and evaluated 2 analogs, the 3,4- and 2,5-dihydroxy derivatives, since these might represent more immediate precursors to the putative biologically active quinone. Both dihydroxy derivatives were more toxic than the parent phenol. The 2,5-dihydroxy derivative was significantly more cytotoxic with a 5-fold decrease in IC50 for both human and B-16 melanoma cells in vitro. In the presence of mushroom tyrosinase, both derivatives were potent inhibitors of isolated DNA polymerase with essentially complete inhibition occurring at concentrations of 10(-5) M. The 3,4-dihydroxy derivative exerted inhibitory effects primarily upon thymidine incorporation into melanoma cells in vitro while the 2,5-dihydroxy derivative also inhibited uridine and leucine incorporation. There was no significant antitumor activity observed in the B-16 system, a fact which might be attributed to the increased toxicity of the compounds.
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