Histochemical differentiation of peroxidase-mediated from tyrosinase-mediated melanin formation in mammalian tissues

Okun, Milton R.; Edelstein, Leon M.; Or, Nur; Hamada, George S.; Donnellan, Barbara; Lever, Walter F.

doi:10.1007/bf00278360

Cited by 56 publications

(19 citation statements)

References 28 publications

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“…Since laccase enzymes have long been recognized to mediate the oxidation of catechols such as L-dopa (Okun et al, 1970), we tested if the activity obtained by electrophoresis was mediated by laccases rather than by PO. When used in reaction mixtures lacking H 2 O 2 , DAB has been found to be a good substrate for laccases.…”

Section: Article In Pressmentioning

confidence: 99%

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA

Zufelato

Lourenço

Simões

et al. 2004

Insect Biochemistry and Molecular Biology

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Section: Article In Pressmentioning

confidence: 99%

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA

Zufelato

Lourenço

Simões

et al. 2004

Insect Biochemistry and Molecular Biology

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“…In the 1970s, Okun et al [7, 8, 9]showed a correlation between peroxidase activity and the ability to oxidize dopa or tyrosine to melanin in such cells. They also demonstrated peroxidase activity in melanoma tumor cells, the melanocytes of blue nevi and normal epidermal melanocytes [10].…”

Section: Melanin Synthesis and The Role Of Peroxidasementioning

confidence: 99%

Peroxidase-Mediated Mechanisms Are Involved in the Melanocytotoxic and Melanogenesis-Inhibiting Effects of Chemical Agents

Kasraee¹

2002

Dermatology

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Melanogenesis is based on the enzymatic conversion of the amino acid tyrosine, through a series of intermediates, to melanin pigments. The nature of the enzymes involved in the different steps of melanogenesis has been intensely debated. However, it is now believed that tyrosinase is responsible for the conversion of tyrosine to dopa and of dopa to dopaquinone, and that peroxidase accomplishes the oxidative polymerization of the eventually formed indoles to eumelanin pigments. Some very few investigators have also considered a main role for peroxidase in initiating melanogenesis. At present, most different hypotheses are focused on tyrosinase-mediated mechanisms to elucidate the melanocytotoxic and depigmenting activities of chemicals. However, many properties of these agents cannot be explained by such mechanisms. Most of the melanocytotoxic agents (e.g. hydroquinone, catechols, butylated hydroxyanisole) can be converted to cytotoxic species, such as quinones, by the peroxidase-H₂O₂ system. On the other hand, many of the melanogenesis inhibitors which are not known to inhibit tyrosinase (e.g. glucocorticoids, ascorbic acid, indomethacin) have the capacity to strongly inhibit peroxidase activity. We have proposed that peroxidase-mediated mechanisms, in addition to or in several instances rather than tyrosinase-mediated mechanisms, can explain the melanocytotoxic and depigmenting properties of such agents.

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“…In addition, it is known that the DOPA oxidase reaction in the L-B method can result in non-specific false-positive reactions due to auto-oxidation and/or internal peroxidase [10,11]. False-positive reactions with other oxidations were also observed in the other classical DOPA oxidase reactions.…”

Section: Discussionmentioning

confidence: 99%

New Methodological Approach for the Rapid and Sensitive Detection of Melanocytes and Melanocytic Tumours

et al. 2009

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Background: During melanogenesis, the activity of tyrosinase (the key enzyme for melanin synthesis) is important in the diagnosis of melanomas. Methods: Nine samples were included in this study, based on the availability of four malignant melanomas and five benign tumours. Our new approach is based on a combination of the DOPA oxidase and the glyoxylic acid (GA) methods for catecholamine (named the ‘DOPA-GA method’). Here, we compared the conventional DOPA oxidase method with that of the DOPA-GA method. Results: In all malignant melanomas, the fluorescence intensity of the DOPA-GA method was strongly expressed within the cytoplasm. The melanoma cells showed an obvious sensitivity compared with the Laidlaw and Blackberg method, as did the melanocytes in the normal skin. Detection was easier with the DOPA-GA method than the Laidlaw and Blackberg method. Hence, we developed a sensitive and rapid method with a total assay time of less than 30 min. Conclusion: DOPA-GA reflects tyrosinase activity in melanocytic tumours, and our new approach is an improvement on the conventional DOPA oxidase method, with regard to both specificity and sensitivity. The DOPA-GA method will be useful for routine pathological testing and melanogenetic studies of melanocytes and melanocytic tumours.

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Histochemical differentiation of peroxidase-mediated from tyrosinase-mediated melanin formation in mammalian tissues

Cited by 56 publications

References 28 publications

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA

Peroxidase-Mediated Mechanisms Are Involved in the Melanocytotoxic and Melanogenesis-Inhibiting Effects of Chemical Agents

New Methodological Approach for the Rapid and Sensitive Detection of Melanocytes and Melanocytic Tumours

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