Institute for Specific Prophylaxis and Tropical Medicine Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Kinderspitalgasse 15, A-1090, Vienna, Austria.
Institute of Medical Microbiology, Faculty of Medicine, University of Szeged, 10 Dóm Square, H-6720, Szeged, Hungary.
Anaerobe. 2022 Feb;73:102507. doi: 10.1016/j.anaerobe.2021.102507. Epub 2021 Dec 31.
Bacteroides fragilis has a pronounced ability to survive prolonged exposure to atmospheric oxygen. The major objective of this study was to biochemically characterize the components of the thioredoxin system in B. fragilis. The nitroreductase activity of TrxR was also assayed.
Components of the thioredoxin system were expressed in E. coli and used in a disulfide reductase activity assay. Activity of TrxR was measured with purified recombinant enzyme or with cell extracts after or without exposure to oxygen or hydrogen peroxide, respectively.
Of all six thioredoxins tested, only thioredoxins A, D, and F were reduced by recombinant TrxR and natural TrxR present in B. fragilis cell extracts. Exposure to oxygen and hydrogen peroxide increased the activity of TrxR. Further, B. fragilis TrxR acts as a nitroreductase with furazolidone or 1-Chloro-2,4-dinitrobenzene as substrates but cannot reduce metronidazole.
TrxR shows an increase in activity under the conditions of oxidative stress and exerts nitroreductase activity.
脆弱拟杆菌具有显著的耐受长时间暴露于大气氧的能力。本研究的主要目的是对脆弱拟杆菌的硫氧还蛋白系统的组成成分进行生化表征。还测定了 TrxR 的硝基还原酶活性。
在大肠杆菌中表达硫氧还蛋白系统的成分，并用于二硫键还原酶活性测定。使用纯化的重组酶或分别在暴露于氧气或过氧化氢前后的细胞提取物来测量 TrxR 的活性。
在所测试的所有 6 种硫氧还蛋白中，只有硫氧还蛋白 A、D 和 F 可被重组 TrxR 和脆弱拟杆菌细胞提取物中存在的天然 TrxR 还原。暴露于氧气和过氧化氢会增加 TrxR 的活性。此外，脆弱拟杆菌 TrxR 可作为硝基还原酶，以 furazolidone 或 1-氯-2,4-二硝基苯作为底物，但不能还原甲硝唑。
TrxR 在氧化应激条件下表现出活性增加，并发挥硝基还原酶活性。
