Ommochromes are widespread pigments that mediate multiple functions in invertebrates. The two main families of ommochromes are ommatins and ommins, which both originate from the kynurenine pathway but differ in their backbone, thereby in their coloration and function. Despite its broad significance, how the structural diversity of ommochromes arises in vivo has remained an open question since their first description. In this study, we combined organic synthesis, analytical chemistry and organelle purification to address this issue. From a set of synthesized ommatins, we derived a fragmentation pattern that helped elucidating the structure of new ommochromes. We identified uncyclized xanthommatin as the elusive biological intermediate that links the kynurenine pathway to the ommatin pathway within ommochromasomes, the ommochrome-producing organelles. Due to its unique structure, we propose that uncyclized xanthommatin functions as a key branching metabolite in the biosynthesis and structural diversification of ommatins and ommins, from insects to cephalopods.

Ommochromes是广泛存在的颜料，可在无脊椎动物中介导多种功能。ommochromes的两个主要家族是ommatins和ommins，它们都起源于犬尿氨酸途径，但其主链有所不同，因此其颜色和功能也不同。尽管它具有广泛的意义，但体内如何发生全色素的结构多样性自从第一次描述以来，它仍然是一个未解决的问题。在这项研究中，我们结合了有机合成，分析化学和细胞器纯化来解决这个问题。从一组合成的ommatins中，我们获得了有助于阐明新ommochromes结构的片段化模式。我们确定未环化的黄体素是一种难以捉摸的生物中间体，该化学中间体将犬尿氨酸途径连接至全色素体（产生全色素的细胞器）内的全色素途径。由于其独特的结构，我们建议未环化的黄体素在ommatins和ommins的生物合成和结构多样化（从昆虫到头足类）中起关键的分支代谢产物的作用。