中性 pH 值和铜离子在后儿茶酚阶段促进真黑素生成。

Neutral pH and copper ions promote eumelanogenesis after the dopachrome stage.

机构信息

Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.

出版信息

Pigment Cell Melanoma Res. 2013 Nov;26(6):817-25. doi: 10.1111/pcmr.12137. Epub 2013 Aug 5.

Abstract

The diversity of pigmentation in the skin, hair, and eyes of humans has been largely attributed to the diversity of pH in melanosomes with acidic pH being proposed to suppress melanin production. Tyrosinase has an optimum pH of 7.4 and its activity is suppressed greatly at lower pH values. The first step of eumelanogenesis is the oxidation of tyrosine to dopachrome (DC) via dopaquinone. However, how eumelanogenesis is controlled by pH beyond this stage is not known. In this study, we examined the effects of pH (5.3-7.3) on the conversion of DC to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and the subsequent oxidation of DHI and DHICA to form eumelanin. The effects of Cu(2+) ions on those reactions were also compared. The results indicate that an acidic pH greatly suppresses the late stages of eumelanogenesis and that Cu(2+) ions accelerate the conversion of DC to DHICA and its subsequent oxidation.

摘要

人类皮肤、头发和眼睛的色素沉着多样性在很大程度上归因于黑素小体的 pH 值多样性，而酸性 pH 值被认为可以抑制黑色素的产生。酪氨酸酶的最适 pH 值为 7.4，其活性在较低 pH 值下会大大受到抑制。真黑素生成的第一步是通过多巴醌将酪氨酸氧化为多巴色素（DC）。然而，在此阶段之后，pH 值如何控制真黑素生成尚不清楚。在这项研究中，我们研究了 pH 值（5.3-7.3）对 DC 转化为 5,6-二羟基吲哚（DHI）和 5,6-二羟基吲哚-2-羧酸（DHICA）以及随后的 DHI 和 DHICA 氧化形成真黑素的影响。还比较了 Cu(2+) 离子对这些反应的影响。结果表明，酸性 pH 值极大地抑制了真黑素生成的后期阶段，而 Cu(2+) 离子加速了 DC 向 DHICA 的转化及其随后的氧化。