RATIONALE N-β-Alanyldopamine (NBAD) and N-acetyldopamine (NADA) are catecholamines that are used by insects as sclerotizing precursors to harden their cuticle. They share a common pathway utilizing the same set of sclerotizing enzymes. Yet, cuticles using NBAD are brown, while cuticles using NADA are colorless. To identify the cause of this major unresolved color difference, molecular transformations of NBAD with cuticular enzymes were investigated. METHODS Reactions of NBAD and NADA with native cuticle isolated from the wandering stages of Sarcophaga bullata larvae as well as the reactions of NBAD with cuticular sclerotization enzymes - phenoloxidase, quinone isomerase and quinone methide isomerase - were investigated using UV-Vis spectroscopy, high-performance liquid chromatography (HPLC), and mass spectrometry (MS). In addition, the reactivity of enzymatically generated NBAD quinone was investigated by MS. RESULTS Reactions of NBAD with sclerotizing enzymes isolated from Sarcophaga bullata larvae generate colorless products such as N-β-alanylnorepinephrine, N-β-alanylarterenone, dehydro NBAD, the benzodioxan dimers of dehydro NBAD and other minor adducts, the same kind of compounds generated by NADA reaction with cuticular enzymes. However, oxidation of NBAD produces colored quinone adducts, in addition. NADA, which lacks the amino group, did not produce these quinone adducts. CONCLUSIONS LC/MS analysis of the reaction mixture of NBAD-cuticular enzyme reactions reveals the novel production of colored quinone adducts that are not possible for NADA. Therefore, our results suggest that the brown coloration of cuticle formed through NBAD crosslinking is likely due to the formation and accumulation of NBAD quinone and its adducts, while NADA quinone adducts tend not to form during NADA crosslinking, producing a nearly colorless cuticle.

中文翻译：

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揭示N-β-丙氨酰多巴胺的复杂分子转化，该分子转化导致昆虫表皮呈棕色。

RATIONALEN-β-阿拉尼多巴胺（NBAD）和N-乙酰基多巴胺（NADA）是儿茶酚胺，被昆虫用作硬化前体以硬化其表皮。它们使用同一组硬化酶共有一条共同的途径。但是，使用NBAD的表皮是棕色，而使用NADA的表皮是无色的。为了确定这种未解决的主要色差的原因，研究了表皮酶对NBAD分子的转化。方法利用紫外-可见光谱法，高效能法研究了NBAD和NADA与天然分离的角质层（Sarcophaga bullata幼虫）游走的表皮的反应以及NBAD与表皮硬化酶酚氧化酶，醌异构酶和醌甲基化异构酶的反应。液相色谱（HPLC）和质谱（MS）。此外，MS研究了酶促生成的NBAD醌的反应性。结果NBAD与分离自牛Sar的幼虫的硬化酶的反应生成无色产物，例如N-β-丙氨酰去甲肾上腺素，N-β-丙氨酰肾上腺素，脱氢NBAD，脱氢NBAD的苯并二恶烷二聚体和其他次要加合物，与由化合物生成的同类化合物NADA与表皮酶反应。但是，NBAD的氧化还会产生有色的醌加合物。缺少氨基的NADA没有产生这些醌加合物。结论LC / MS对NBAD-表皮酶反应混合物的分析表明，新型的有色醌加合物的生产对于NADA而言是不可能的。所以，