Saul S, Sugumaran M
Department of Biology, University of Massachusetts, Boston 02125.
FEBS Lett. 1988 Sep 12;237(1-2):155-8. doi: 10.1016/0014-5793(88)80191-1.
Insoluble cuticle-bound enzyme(s) of Manduca sexta pharate pupae, which is known to convert N-acetyldopamine to N-acetylnorepinephrine through the intermediate formation of quinone methide, also converted exogenously supplied N-acetyldopamine quinone to N-acetylnorepinephrine. The presence of a quinone trap such as N-acetylcysteine in the reaction mixture containing N-acetyldopamine and cuticle prevented the formation of N-acetylnorepinephrine but readily yielded N-acetylcysteine-N-acetyldopamine quinone adduct as a dead-end product. These results indicate the oxidation of N-acetyldopamine to its quinone and its enzyme-catalyzed isomerization to quinone methide before yielding N-acetylnorepinephrine as the stable product. The role of this newly discovered isomerase in sclerotization of insect cuticle is discussed.
烟草天蛾化蛹前期蛹体中不溶性的表皮结合酶，已知其通过醌甲基化物的中间形成过程将N - 乙酰多巴胺转化为N - 去甲肾上腺素，该酶也能将外源供应的N - 乙酰多巴胺醌转化为N - 去甲肾上腺素。在含有N - 乙酰多巴胺和表皮的反应混合物中存在醌捕获剂（如N - 乙酰半胱氨酸）时，可阻止N - 去甲肾上腺素的形成，但很容易产生N - 乙酰半胱氨酸 - N - 乙酰多巴胺醌加合物作为终产物。这些结果表明，N - 乙酰多巴胺先氧化为其醌，然后在产生稳定产物N - 去甲肾上腺素之前，酶催化其异构化为醌甲基化物。本文讨论了这种新发现的异构酶在昆虫表皮硬化过程中的作用。
