Melanins are widely distributed in animals and plants; in vertebrates, most melanins are present on the body surface. The diversity of pigmentation in vertebrates is mainly attributed to the quantity and ratio of eumelanin and pheomelanin synthesis. Most natural melanin pigments in animals consist of both eumelanin and pheomelanin in varying ratios, and thus, their combined synthesis is called “mixed melanogenesis.” Gene expression is an established mechanism for controlling melanin synthesis; however, there are multiple factors that affect melanin synthesis besides gene expression. Due to the differential sensitivity of the eumelanin and pheomelanin synthetic pathways to pH, melanosomal pH likely plays a major role in mixed melanogenesis. Here, we focused on various factors affecting mixed melanogenesis including (1) chemical regulation of melanin synthesis, (2) melanosomal pH regulation during normal melanogenesis and effect on mixed melanogenesis, and (3) mechanisms of melanosomal pH control (proton pumps, channels, transporters, and signaling pathways).

中文翻译：

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皮肤色素沉着的化学和生化控制，特别强调混合黑色素生成

黑色素广泛分布于动植物中；在脊椎动物中，大多数黑色素存在于体表。脊椎动物色素沉着的多样性主要归因于真黑素和褐黑素合成的数量和比例。动物中的大多数天然黑色素色素由不同比例的真黑素和褐黑素组成，因此，它们的组合合成被称为“混合黑色素生成”。基因表达是控制黑色素合成的既定机制；然而，除了基因表达之外，还有多种因素会影响黑色素的合成。由于真黑素和褐黑素合成途径对 pH 的不同敏感性，黑素体 pH 可能在混合黑素生成中起主要作用。这里，