Nature ( IF 50.5 ) Pub Date : 2024-02-07 , DOI: 10.1038/s41586-024-07017-8
Douglas V Guzior 1, 2 , Maxwell Okros 1 , Madison Shivel 1, 3 , Bruin Armwald 1, 3 , Christopher Bridges 1, 2 , Yousi Fu 1 , Christian Martin 1 , Anthony L Schilmiller 4 , Wendy M Miller 5, 6 , Kathryn M Ziegler 5, 6 , Matthew D Sims 5, 6 , Michael E Maddens 5, 6 , Stewart F Graham 5, 6, 7 , Robert P Hausinger 1, 2 , Robert A Quinn 1
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Bile acids (BAs) are steroid detergents in bile that contribute to the absorption of fats and fat-soluble vitamins while shaping the gut microbiome because of their antimicrobial properties1,2,3,4. Here we identify the enzyme responsible for a mechanism of BA metabolism by the gut microbiota involving amino acid conjugation to the acyl-site of BAs, thus producing a diverse suite of microbially conjugated bile acids (MCBAs). We show that this transformation is mediated by acyltransferase activity of bile salt hydrolase (bile salt hydrolase/transferase, BSH/T). Clostridium perfringens BSH/T rapidly performed acyl transfer when provided various amino acids and taurocholate, glycocholate or cholate, with an optimum at pH 5.3. Amino acid conjugation by C. perfringens BSH/T was diverse, including all proteinaceous amino acids except proline and aspartate. MCBA production was widespread among gut bacteria, with strain-specific amino acid use. Species with similar BSH/T amino acid sequences had similar conjugation profiles and several bsh/t alleles correlated with increased conjugation diversity. Tertiary structure mapping of BSH/T followed by mutagenesis experiments showed that active site structure affects amino acid selectivity. These MCBA products had antimicrobial properties, where greater amino acid hydrophobicity showed greater antimicrobial activity. Inhibitory concentrations of MCBAs reached those measured natively in the mammalian gut. MCBAs fed to mice entered enterohepatic circulation, in which liver and gallbladder concentrations varied depending on the conjugated amino acid. Quantifying MCBAs in human faecal samples showed that they reach concentrations equal to or greater than secondary and primary BAs and were reduced after bariatric surgery, thus supporting MCBAs as a significant component of the BA pool that can be altered by changes in gastrointestinal physiology. In conclusion, the inherent acyltransferase activity of BSH/T greatly diversifies BA chemistry, creating a set of previously underappreciated metabolites with the potential to affect the microbiome and human health.
中文翻译:
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胆汁盐水解酶酰基转移酶活性扩大了胆汁酸的多样性
胆汁酸 (BA) 是胆汁中的类固醇清洁剂,由于其抗菌特性,有助于脂肪和脂溶性维生素的吸收,同时塑造肠道微生物组1,2,3,4 。在这里,我们确定了负责肠道微生物群 BA 代谢机制的酶,涉及氨基酸与 BA 酰基位点的结合,从而产生多种微生物结合胆汁酸 (MCBA)。我们证明这种转化是由胆盐水解酶(胆盐水解酶/转移酶,BSH/T)的酰基转移酶活性介导的。当提供各种氨基酸和牛磺胆酸盐、甘氨胆酸盐或胆酸盐时,产气荚膜梭菌BSH/T快速进行酰基转移,最适pH为5.3。产气荚膜梭菌BSH/T 的氨基酸缀合是多种多样的,包括除脯氨酸和天冬氨酸之外的所有蛋白质氨基酸。 MCBA 的生产在肠道细菌中广泛存在,并使用特定菌株的氨基酸。具有相似 BSH/T 氨基酸序列的物种具有相似的接合特征,并且几个bsh/t等位基因与增加的接合多样性相关。 BSH/T 的三级结构图谱和诱变实验表明活性位点结构影响氨基酸选择性。这些 MCBA 产品具有抗菌特性,氨基酸疏水性越高,抗菌活性就越高。 MCBA 的抑制浓度达到了哺乳动物肠道中天然测量的浓度。喂给小鼠的 MCBA 进入肠肝循环,其中肝脏和胆囊的浓度根据结合氨基酸的不同而变化。 对人类粪便样本中的 MCBA 进行定量显示,它们的浓度等于或大于次级和初级 BA,并且在减肥手术后降低,从而支持 MCBA 作为 BA 库的重要组成部分,可以通过胃肠道生理学的变化而改变。总之,BSH/T 固有的酰基转移酶活性极大地多样化了 BA 化学,产生了一系列以前未被充分认识的代谢物,有可能影响微生物组和人类健康。