Sugumaran M
Department of Biology, University of Massachusetts, Boston 02125.
FEBS Lett. 1991 Dec 16;295(1-3):233-9. doi: 10.1016/0014-5793(91)81431-7.
Melanogenesis is an important biochemical process for the production of skin pigments which protect many animals from the damage of solar radiation. The abnormalities in melanogenesis are associated with albinism, vitiligo, as well as malignant melanoma in humans. In the lower forms of animals viz., insects, the exoskeleton is hardened to protect their soft bodies by a process called sclerotization, which is often accompanied by melanization. Recent advances in the biochemistry of sclerotization and melanization reveal remarkable similarity between these two processes. The seven stages of sclerotization are: (a) enzymatic oxidation of N-acyldopamine, (b) Michael-1,4-addition reactions of N-acyldopamine quinone, (c) tautomerization of quinone to quinone methide, (d) Michael-1,6-addition of quinone methides, (e) tautomerization of N-acyldopamine quinone methide to 1,2-dehydro-N-acyldopamine, (f) enzymatic oxidation of 1,2-dehydro-N-acyldopamine, and (g) the reactions of resultant quinonoid compounds. Amazingly, striking similarities in the reaction sequences are found in the melanization process starting from dopa. These comparisons predict a central role for quinone methides as reactive intermediates during melanization. Accordingly, recent studies provide increasing evidence in favor of this proposition.
黑色素生成是一种重要的生物化学过程，用于产生皮肤色素，这些色素可保护许多动物免受太阳辐射的伤害。黑色素生成异常与人类的白化病、白癜风以及恶性黑色素瘤有关。在较低等的动物（如昆虫）中，外骨骼通过一种称为硬化的过程变硬，以保护其柔软的身体，而硬化过程通常伴随着黑化。硬化和黑化生物化学方面的最新进展揭示了这两个过程之间的显著相似性。硬化的七个阶段为：（a）N - 酰基多巴胺的酶促氧化，（b）N - 酰基多巴胺醌的迈克尔1,4 - 加成反应，（c）醌向醌甲基化物的互变异构，（d）醌甲基化物的迈克尔1,6 - 加成，（e）N - 酰基多巴胺醌甲基化物向1,2 - 脱氢 - N - 酰基多巴胺的互变异构，（f）1,2 - 脱氢 - N - 酰基多巴胺的酶促氧化，以及（g）所得醌类化合物的反应。令人惊讶的是，在从多巴开始的黑化过程中发现了反应序列中的惊人相似之处。这些比较预测醌甲基化物在黑化过程中作为反应中间体起着核心作用。因此，最近的研究提供了越来越多支持这一观点的证据。
