Melanin plays an important role in the protection of the skin from ultraviolet irradiation. However, excessive melanin deposition leads to hyperpigmentation and freckles, which are recognized as skin problems, and signs of aging. Tyrosinase, a copper-containing protein, is the rate-limiting enzyme in melanin biosynthesis and first catalyzes the hydroxylation of l-tyrosine to 3,4-dihydroxyphenylalanine (DOPA) and the further oxidization to dopaquinone. To assist the proper regulation of melanin production, we screened compounds and found that 5,6,7,8-tetrahydro-4H-furo[3,2-c]azepine-4-thione (T4FAT), a thioamide derivative, inhibited melanogenesis in B16F10 mouse melanoma cells. T4FAT was not toxic to cells and was stable in water; in addition, it inhibited the activity of tyrosinase derived from mushroom and B16F10 cells in a non-competitive manner. T4FAT downregulated tyrosinase protein expression in B16F10 cells without affecting mRNA expression. As copper binding to the tyrosinase protein is required for both enzymatic activity, correct folding, and maturation, we examined the metal-chelating activities of T4FAT. Equimolar amount of T4FAT resulted in almost complete chelation of copper ions. The thioamide group of T4FAT is essential for copper chelation and tyrosinase inhibition, which subsequently resulted in melanogenesis inhibition in B16F10 cells. Although T4FAT has similar in vitro properties to kojic acid, which is also a copper chelator and approved as a component of cosmetic formulations, T4FAT inhibited melanogenesis in B16F10 cells 30 times more efficiently than kojic acid. These results suggested that T4FAT, a novel copper chelator, may be helpful for the development of new cosmetics for skin whitening.

中文翻译：

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Azepine衍生物T4FAT是一种新型的铜螯合剂，可抑制酪氨酸酶。

黑色素在保护皮肤免受紫外线照射中起重要作用。但是，过多的黑色素沉积会导致色素沉着过度和雀斑，这被认为是皮肤问题和衰老迹象。酪氨酸酶是一种含铜的蛋白质，是黑色素生物合成中的限速酶，首先催化1-酪氨酸羟基化为3,4-二羟基苯丙氨酸（DOPA），然后进一步氧化为多巴醌。为了帮助适当调节黑色素的产生，我们筛选了化合物，发现5,6,7,8-四氢-4H-呋喃并[3,2-c]氮杂-4-硫酮（T4FAT），一种硫酰胺衍生物，抑制黑色素生成。在B16F10小鼠黑色素瘤细胞中 T4FAT对细胞无毒，在水中稳定。此外，它以非竞争性方式抑制了蘑菇和B16F10细胞产生的酪氨酸酶活性。T4FAT下调B16F10细胞中酪氨酸酶蛋白表达，而不会影响mRNA表达。由于铜与酪氨酸酶蛋白的结合对于酶活性，正确折叠和成熟都是必需的，因此我们研究了T4FAT的金属螯合活性。等摩尔量的T4FAT导致铜离子几乎完全螯合。T4FAT的硫酰胺基对于铜螯合和酪氨酸酶抑制至关重要，随后会导致B16F10细胞的黑色素生成抑制。尽管T4FAT的体外特性与曲酸（也是铜螯合剂并被批准用作化妆品制剂的成分）具有相似的体外特性，但T4FAT抑制B16F10细胞中黑色素生成的效率是曲酸的30倍。