Molecular mechanisms for mammalian melanogenesis Comparison with insect cuticular sclerotization

摘要

>Melanogenesis is an important biochemical process for the production of skin pigments which protect many animals from the damage of s?? radiation. The abnormalities in melanogenesis are associated with albinism, vitiligo, as well as malignant melanoma in humans. In the lower f??? of animals viz., insects, the exoskeleton is hardened to protect their soft bodies by a process called sclerotization, which is often accompanie?? melanization. Recent advances in the biochemistry of sclerotization and melanization reveal remarkable similarity between these two proce?? The seven stages of sclerotization are: (a) enzymatic oxidation of N-acyldopamine, (b) Michael-1,4-addition reactions of N-acyldopamine quin?? (c) tautomerization of quinone to quinone methide, (d) Michael-1,6-addition of quinone methides, (e) tautomerization of N-acyldopamine qui?? methide to 1,2-dehydro-N-acyldopamine, (f) enzymatic oxidation of 1,2-dehydro-N-acyldopamine, and (g) the reactions of resultant quino?? compounds. Amazingly, striking similarities in the reaction sequences are found in the melanization process starting from dopa. These compari?? predict a central role for quinone methides as reactive intermediates during melanization. Accordingly, recent studies provide increasing evid?? in favor of this proposition.