Metalloenzyme Research Group and Department of Plant Science and Technology, Chung-Ang University, Anseong 17546, Republic of Korea.
J Microbiol Biotechnol. 2023 Dec 28;33(12):1606-1614. doi: 10.4014/jmb.2308.08021. Epub 2023 Sep 21.
Biochemical gut metabolism of dietary bioactive compounds is of great significance in elucidating health-related issues at the molecular level. In this study, a human gut bacterium cleaving C-C glycosidic bond was screened from puerarin conversion to daidzein, and a new, gram-positive -glycoside-deglycosylating strain, sp. MRG-IFC3, was isolated from human fecal sample under anaerobic conditions. Though MRG-IFC3 biotransformed isoflavone -glycoside, it could not metabolize other -glycosides, such as vitexin, bergenin, and aloin. As evident from the production of the corresponding aglycons from various 7--glucosides, MRG-IFC3 strain also showed 7--glycoside cleavage activity; however, flavone 3--glucoside icariside II was not metabolized. In addition, for mechanism study, -glycosyl bond cleavage of puerarin by MRG-IFC3 strain was performed in DO GAM medium. The complete deuterium enrichment on C-8 position of daidzein was confirmed by H NMR spectroscopy, and the result clearly proved for the first time that daidzein is produced from puerarin. Two possible reaction intermediates, the quinoids and 8-dehydrodaidzein anion, were proposed for the production of daidzein-8d. These results will provide the basis for the mechanism study of stable -glycosidic bond cleavage at the molecular level.
膳食生物活性化合物的生化肠道代谢在阐明分子水平上的健康相关问题方面具有重要意义。在这项研究中，从葛根素转化为大豆苷元的过程中筛选出一种能够裂解 C-C 糖苷键的肠道细菌，并从人类粪便样本中在厌氧条件下分离出一种新的革兰氏阳性糖苷脱糖基化菌株， sp. MRG-IFC3。虽然 MRG-IFC3 可以转化异黄酮糖苷，但它不能代谢其他糖苷，如牡荆素、 Bergenin 和芦荟苷。从各种 7--葡萄糖苷产生相应的糖苷配基可以明显看出，MRG-IFC3 菌株还表现出 7--糖苷裂解活性；然而，黄酮 3--葡萄糖苷 icariside II 不能被代谢。此外，为了进行机制研究，在 DO GAM 培养基中进行了 MRG-IFC3 菌株对葛根素 - 糖苷键的裂解。通过 H NMR 光谱证实了大豆苷元 C-8 位上完全氘富集，这一结果首次清楚地证明了大豆苷元是由葛根素产生的。提出了两种可能的反应中间体，醌和 8-脱氢大豆苷元阴离子，用于产生大豆苷元-8d。这些结果将为稳定 - 糖苷键在分子水平上的裂解机制研究提供基础。
