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Cited by 156melanin and skin pigmentationMelanoma and MAPK PathwaysCalcium signaling and nucleotide metabolism

Regulation of the Catalytic Activity of Preexisting Tyrosinase in Black and Caucasian Human Melanocyte Cell Cultures

Fuller, Bryan B., Spaulding, Deborah T., Smith, Dustin R.·2001·Experimental Cell Research
DOI 10.1006/excr.2000.5092
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Abstract

The activity of tyrosinase, the rate-limiting enzyme for melanin synthesis, is higher in Black skin melanocytes than in melanocytes derived from Caucasian skin. This variation in enzyme activity is not due to differences in tyrosinase abundance or tyrosinase gene activity, but, rather, is due to differences in the catalytic activity of preexisting tyrosinase. In melanocytes, tyrosinase is localized to the membrane of melanosomes and in Caucasian melanocytes the melanosome-bound enzyme is largely inactive. Conversely, in melanosomes of Black melanocytes, tyrosinase has high catalytic activity. Treatment of Caucasian melanocytes with the lysosomotropic compound ammonium chloride or with the ionophores nigericin and monensin results in a rapid and pronounced increase in tyrosinase activity. This increase occurs without any change in tyrosinase abundance, indicating that these compounds are increasing the catalytic activity of preexisting enzyme. Inhibition of the vacuolar proton pump V-ATPase by treatment of Caucasian melanocytes with bafilomycin also increases tyrosinase activity. In contrast to the 10-fold increase in tyrosinase observed in Caucasian melanocytes, neither ammonium chloride, monensin, nigericin, nor bafilomycin is able to increase the already high level of tyrosinase activity present in melanosomes of melanocytes derived from Black skin. Finally, staining of Caucasian melanocytes with the fluorescent weak base acridine orange shows that melanosomes of Caucasian, but not Black, melanocytes are acidic organelles. These data support a model for racial pigmentation that is based on differences in melanosome pH in Black and Caucasian skin types. The models suggests that melanosomes of Caucasian melanocytes are acidic, while those of Black individuals are more neutral. Since tyrosinase is inactive in an acid environment, the enzyme is largely inactive in Caucasian melanosomes but fully active in Black melanosomes.

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Authors
Fuller, B. B., Spaulding, D. T., & Smith, D. R.
Affiliations
University of Oklahoma Health Sciences Center (US)
Venue
Experimental Cell Research
Publisher
Elsevier BV
Published
2001-01
Volume
262
Issue
2
Pages
197-208
ISSN
0014-4827 (ISSN-L)
DOI
10.1006/excr.2000.5092
OpenAlex
W2092163284
Cited by
156
References
42
Citations by year
2026: 3 · 2025: 4 · 2024: 4 · 2023: 3 · 2022: 3 · 2021: 8 · 2020: 5 · 2019: 5 · 2018: 9 · 2017: 4 · 2016: 5 · 2015: 5 · 2014: 8 · 2013: 5 · 2012: 2
FWCI
2.94
Type
journal article
Language
en
Open access
closed
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Experimental Cell Research (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Melanoma and MAPK Pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Physiology › Calcium signaling and nucleotide metabolism
Keywords
tyrosinase, melanocytes, melanogenesis, enzyme activity, melanosomes, lysosomotropic agents, ammonium chloride, nigericin, monensin, V-ATPase, bafilomycin
MeSH terms
Acridine Orange, Ammonium Chloride, Anti-Bacterial Agents, Catalysis, Cell Survival, Cells, Cultured, Dose-Response Relationship, Drug, Electrophoresis, Polyacrylamide Gel, Enzyme Activation, Enzyme Inhibitors, Humans, Hydrogen-Ion Concentration, Male, Melanocytes, Monensin, Nigericin, Skin Pigmentation, Monophenol Monooxygenase, Blotting, Western, Macrolides, Melanosomes, Black People, White People

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