Letter | Published:

Are Tyrosinase and Thiol Groups Present in Skin Epithelium?

Naturevolume 166page110 (1950) | Download Citation



WHEN an aqueous solution of 1:2:4-trihydroxynaphthalene (dihydrolawsone) is applied to the skin, immediate oxidation to the orange-yellow 2-hydroxy-1:4-naphthaquinone (lawsone) (I) occurs, presumably because of the presence in the skin of an oxidase system. This enzyme is undoubtedly a polyphenoloxidase; but since similar application of L-tyrosine, DL-3:4-dihydroxyphenylalanine, or catechol does not lead to the production of any colour, it is extremely unlikely that the enzyme is tyrosinase. It is known1 that quinones react rapidly with thiol compounds, and it does not appear unreasonable to suppose that, if human skin contains free SH-groups, these would react with the lawsone deposited in situ in the above manner. If the lawsone is allowed to remain on the skin for twenty-four hours, the stain can be removed almost completely by washing with soap and water. Consequently skin appears to contain very few thiol groups.

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  1. 1

    Fieser and Fieser, “Organic Chemistry”, 738 (1944).

  2. 2

    Compare Burton and Stoves, Nature, 165, 569 (1950).

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  1. King's College of Household and Social Science, University of London, London, W.8

    • H. BURTON
    •  & J. M. WILLIAMS


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