Structural Basis for Hormone and Neurotransmitter Processing by Gut Microbial Enzymes

摘要 深度测序和灵知生物动物模型系统的突破已经确立了肠道 微生物区系，即生活在胃肠道内的数万亿细菌，在正常的 哺乳动物的生理学和向疾病的转变。然而，微生物催化的确切反应 酶及其对哺乳动物组织的影响仍然知之甚少。微生物的研究进展 酶是具有挑战性的，因为肠道微生物群编码大约500万种蛋白质，而不是蛋白质组 这很容易解决。正如这里所概述的，我们专注于一组特定的肠道微生物酶，这些酶 在逆转哺乳动物代谢过程中发挥关键作用，这些代谢过程在对一系列 治疗剂。这些微生物酶没有与它们的哺乳动物宿主共同进化来处理药物； 相反，它们自然作用于大量未激活的激素和神经递质的代谢物 直抵内脏。在这个提案中，我们集中讨论两种荷尔蒙，一种主要的循环甲状腺激素 甲状腺激素和促进癌症的类固醇雌酮，以及一种神经递质，5-羟色胺，这些都是 由二期药物代谢UDP-葡萄糖醛酸基转移酶处理，附着失活 葡萄糖醛酸糖部分，用来标记这些化合物的排泄。甲状腺素、雌酮和5-羟色胺 代谢物以葡萄糖醛酸苷结合的形式到达肠道，并受到我们项目重点的重新激活 -肠道微生物组编码的b-葡萄糖醛酸苷酶(GUS)酶，可分解葡萄糖醛酸糖。 我们开创了肠道微生物GUS酶的研究先河，并确定了它们在药物中扮演的角色 有效性和毒性，并开发了GUS靶向抑制剂，改善了对 动物模型。我们还表明，在人类肠道微生物组中有279个独特的GUS同源基因。 在这里，我们最重要的假设是，人类肠道微生物群编码了一系列结构上-和 功能不同的GUS酶，能够作用于化学离散的内生葡萄糖醛酸苷 底物和这些酶对新的化学类型或现有的选择性抑制很敏感 毒品。我们将通过完成三个目标来验证这些假设，这些目标集中在生物内生-葡萄糖醛酸苷 甲状腺激素、雌激素和神经递质的结合物。我们所取得的结果将至关重要 促进我们对人体组织和微生物区系之间的化学串扰的基本理解 可能导致治疗激素失衡、癌症、肠道健康、心血管疾病的新方法 疾病，甚至心理障碍。

Abstract Breakthroughs in deep-sequencing and gnotobiotic animal model systems have established that the gut microbiota, the trillions of bacteria that live within the gastrointestinal tract, play important roles in normal mammalian physiology and transitions to disease. However, the exact reactions catalyzed by microbial enzymes and their influence on mammalian tissues still remain poorly understood. The study of microbial enzymes is challenging because the gut microbiome encodes roughly five million proteins – not a proteome that can be tackled easily. As outlined here, we have focused on a specific set of gut microbial enzymes that play critical roles in reversing mammalian metabolic processes that are crucial in responses to a range of therapeutic agents. These microbial enzymes did not co-evolve with their mammalian hosts to process drugs; instead, they naturally act on the abundant inactivated metabolites of hormones and neurotransmitters that reach the gut. In this proposal, we concentrate on two hormones, the primary circulating thyroid hormone thyroxine and the cancer-promoting steroid estrone, and one neurotransmitter, serotonin, that are all processed by Phase II drug metabolizing UDP-glucuronosyltransferase enzymes that attach inactivating glucuronic acid sugar moieties to mark these compounds for excretion. Thyroxine, estrone, and serotonin metabolites reach the gut as glucuronide conjugates and are subject to reactivation by the focus of our project – the intestinal microbiome-encoded b-glucuronidase (GUS) enzymes that cleave off the glucuronic acid sugar. We have pioneered the study of gut microbial GUS enzymes and have established the roles they play in drug efficacy and toxicity, and have developed GUS-targeted inhibitors that improve the treatment of disease in animal models. We have also shown that there are 279 unique GUS orthologs in the human gut microbiome. Here, our overarching hypotheses are that the human gut microbiome encodes a range of structurally – and functionally – distinct GUS enzymes capable of acting on chemically discrete, endobiotic glucuronide substrates and that such enzymes are susceptible to selective inhibition by novel chemotypes or existing drugs. We will test these hypotheses by completing three aims focused on the endobiotic-glucuronide conjugates of thyroid hormones, estrogens, and neurotransmitters. The results we obtain will crucially advance our basic understanding of the chemical crosstalk between human tissues and the microbiota and may lead to novel approaches for the treatment of hormone imbalances, cancer, gut health, cardiovascular disease, and even psychological disorders.