MAMMALIAN TYROSINASE CATALYZES 3 REACTIONS IN THE BIOSYNTHESIS OF MELANIN
MAMMALIAN TYROSINASE CATALYZES 3 REACTIONS IN THE BIOSYNTHESIS OF MELANIN
复制标题
DOI：
10.1126/science.6810464
复制
发表时间：
1982-01-01
期刊：
影响因子：
56.9
通讯作者：
PAWELEK, J
中科院分区：
文献类型：
--
作者：
KORNER, A;PAWELEK, J
黑色素的生物合成是由酪氨酸酶催化酪氨酸氧化成多巴启动的，该反应需要多巴作为辅因子。然后，酪氨酸酶催化多巴脱氢为多巴喹酮。随后的反应可以在体外自发进行。酪氨酸酶是从小鼠黑色素瘤和棕色小鼠皮肤中提纯的，催化哺乳动物黑素合成的第三个反应，即5，6-二羟基吲哚转化为黑色素。这个反应需要多巴作为辅因子，并被酪氨酸抑制。5，6-二羟基吲哚抑制酪氨酸氧化为多巴，因此哺乳动物色素细胞内酪氨酸和5，6-二羟基吲哚的相对浓度能够以一种以前未知的方式调节黑素合成。酪氨酸酶具有独特的性质，可以在一条生化途径内催化三种不同的反应：单酚的羟化、邻苯二酚的脱氢和二羟基吲哚的脱氢。这些反应中的第一个和第三个需要多巴作为辅因子；在第二个反应中，多巴是底物。
The biosynthesis of melanin is initiated by the catalytic oxidation of tyrosine to dopa by tyrosinase in a reaction that requires dopa as a cofactor. Tyrosinase then catalyzes the dehydrogenation of dopa to dopaquinone. The subsequent reactions can proceed spontaneously in vitro. Tyrosinase, purified from murine melanomas and the skins of brown mice, catalyzes a 3rd reaction in mammalian melanogenesis, i.e., the conversion of 5,6-dihydroxyindole to melanochrome. This reaction requires dopa as a cofactor and is inhibited by tyrosine. 5,6-Dihydroxyindole inhibits the oxidation of tyrosine to dopa, so that the relative concentrations of tyrosine and 5,6-dihydroxyindole within the mammalian pigment cell are capable of regulating melanogenesis in a previously unrecognized fashion. Tyrosinase has the unusual property of catalyzing 3 distinct reactions within a single biochemical pathway: the hydroxylation of a monophenol, the dehydrogenation of a catechol and the dehydrogenation of a dihydroxyindole. The 1st and 3rd of these reactions require dopa as a cofactor; in the 2nd reaction, dopa is a substrate.