Zhang Z, Hillas P J, Ortiz de Montellano P R
Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco 94143-0446, USA.
Arch Biochem Biophys. 1999 Mar 1;363(1):19-26. doi: 10.1006/abbi.1998.1056.
The thioredoxin (Trx) and thioredoxin reductase (TR) of Mycobacterium tuberculosis have been expressed in Escherichia coli and shown to reduce peroxides and dinitrobenzenes. The reduction of H2O2 requires both Trx and TR and is more efficient under anaerobic than aerobic conditions. In contrast, cumene hydroperoxide is reduced to cumyl alcohol and acetophenone in a process that requires NADPH and TR but not Trx. Cumene hydroperoxide reduction is partially inhibited by chelation of trace metals in the medium. The reduction of cumene hydroperoxide by TR is more effective under anaerobic than aerobic conditions due to a competing oxidase reaction in which electrons are transferred from TR to O2. Under anaerobic conditions, dinitrobenzenes also serve as electron acceptors and are reduced by TR to nitroanilines, but the enzyme does not reduce mononitrobenzenes or mononitroimidazoles such as metronidazole. The reductive activity of the Trx-TR system may modify the antioxidant defenses of M. tuberculosis.
结核分枝杆菌的硫氧还蛋白（Trx）和硫氧还蛋白还原酶（TR）已在大肠杆菌中表达，并显示出能还原过氧化物和二硝基苯。H2O2的还原需要Trx和TR两者，且在厌氧条件下比需氧条件下更有效。相比之下，氢过氧化异丙苯在一个需要NADPH和TR但不需要Trx的过程中被还原为枯基醇和苯乙酮。培养基中微量金属的螯合会部分抑制氢过氧化异丙苯的还原。由于存在一种竞争氧化酶反应，即电子从TR转移到O2，TR对氢过氧化异丙苯的还原在厌氧条件下比需氧条件下更有效。在厌氧条件下，二硝基苯也作为电子受体，被TR还原为硝基苯胺，但该酶不会还原单硝基苯或单硝基咪唑类药物，如甲硝唑。Trx-TR系统的还原活性可能会改变结核分枝杆菌的抗氧化防御机制。
