Chauhan Radha, Mande Shekhar C
Institute of Microbial Technology, Sector 39-A, Chandigarh 160036, India.
Biochem J. 2002 Oct 1;367(Pt 1):255-61. doi: 10.1042/BJ20020545.
Mycobacterium tuberculosis alkylhydroperoxidase C (AhpC) belongs to the peroxiredoxin family, but unusually contains three cysteine residues in its active site. It is overexpressed in isoniazid-resistant strains of M. tuberculosis. We demonstrate that AhpC is capable of acting as a general antioxidant by protecting a range of substrates including supercoiled DNA. Active-site Cys to Ala mutants show that all three cysteine residues are important for activity. Cys-61 plays a central role in activity and Cys-174 also appears to be crucial. Interestingly, the C174A mutant is inactive, but double mutant C174/176A shows significant revertant activity. Kinetic parameters indicate that the C176A mutant is active, although much less efficient. We suggest that M. tuberculosis AhpC therefore belongs to a novel peroxiredoxin family and might follow a unique disulphide-relay reaction mechanism.
结核分枝杆菌烷基过氧化氢酶C（AhpC）属于过氧化物氧还蛋白家族，但不同寻常的是其活性位点含有三个半胱氨酸残基。它在结核分枝杆菌的异烟肼耐药菌株中过表达。我们证明AhpC能够通过保护包括超螺旋DNA在内的一系列底物而作为一种通用抗氧化剂发挥作用。活性位点半胱氨酸到丙氨酸的突变体表明所有三个半胱氨酸残基对活性都很重要。半胱氨酸-61在活性中起核心作用，半胱氨酸-174似乎也至关重要。有趣的是，C174A突变体无活性，但双突变体C174/176A显示出显著的回复活性。动力学参数表明C176A突变体有活性，尽管效率低得多。因此，我们认为结核分枝杆菌AhpC属于一个新的过氧化物氧还蛋白家族，可能遵循独特的二硫键中继反应机制。
