Department of Gastroenterology, Changhai Hospital, Navy/Second Military Medical University, Shanghai, China.
Shanghai YueXin Life-Science Information Technology Co., Ltd, Shanghai, China.
Nat Commun. 2022 Nov 14;13(1):6955. doi: 10.1038/s41467-022-34364-9.
Enteropeptidase (EP) initiates intestinal digestion by proteolytically processing trypsinogen, generating catalytically active trypsin. EP dysfunction causes a series of pancreatic diseases including acute necrotizing pancreatitis. However, the molecular mechanisms of EP activation and substrate recognition remain elusive, due to the lack of structural information on the EP heavy chain. Here, we report cryo-EM structures of human EP in inactive, active, and substrate-bound states at resolutions from 2.7 to 4.9 Å. The EP heavy chain was observed to clamp the light chain with CUB2 domain for substrate recognition. The EP light chain N-terminus induced a rearrangement of surface-loops from inactive to active conformations, resulting in activated EP. The heavy chain then served as a hinge for light-chain conformational changes to recruit and subsequently cleave substrate. Our study provides structural insights into rearrangements of EP surface-loops and heavy chain dynamics in the EP catalytic cycle, advancing our understanding of EP-associated pancreatitis.
肠肽酶（EP）通过蛋白水解处理胰蛋白酶原，生成催化活性的胰蛋白酶，从而启动肠道消化。EP 功能障碍会导致一系列胰腺疾病，包括急性坏死性胰腺炎。然而，由于缺乏 EP 重链的结构信息，EP 激活和底物识别的分子机制仍不清楚。在这里，我们报道了人 EP 在非活性、活性和底物结合状态下的冷冻电镜结构，分辨率分别为 2.7 到 4.9 Å。观察到 EP 重链用 CUB2 结构域夹住轻链以进行底物识别。EP 轻链 N 端诱导表面环从非活性构象到活性构象的重排，导致 EP 激活。然后，重链充当铰链，使轻链构象发生变化，以募集并随后切割底物。我们的研究提供了 EP 表面环重排和 EP 催化循环中重链动力学的结构见解，加深了我们对 EP 相关胰腺炎的理解。
