Heym B, Alzari P M, Honoré N, Cole S T
Unité de Génétique Moléculaire Bactérienne, Institut Pasteur, Paris, France.
Mol Microbiol. 1995 Jan;15(2):235-45. doi: 10.1111/j.1365-2958.1995.tb02238.x.
The toxicity of the powerful anti-tuberculosis drug isoniazid (INH) is believed to be mediated by the haem-containing enzyme catalase-peroxidase, encoded by the katG gene of Mycobacterium tuberculosis. Compelling evidence for this was obtained by studying a panel of INH-resistant clinical isolates using a novel strategy based on the polymerase chain reaction and single-strand-conformation polymorphism analysis (PCR-SSCP) to detect mutations in katG. In most cases INH resistance was associated with missense mutations while in a small number of strains the gene had been completely, or partially, deleted. The missense mutations fell into two groups, the larger of which contained several independent mutations that affected the N-terminal peroxidase domain of the protein, resulting in the production of a catalase peroxidase with strongly reduced enzyme activity and increased heat liability. The effects of these substitutions could be interpreted by means of molecular modelling using the crystal structure of the related enzyme cytochrome c peroxidase from yeast as a template. The second group comprises a frequently occurring amino acid substitution and a single mutation that are both located in the C-terminal domain but do not noticeably alter either enzyme activity or heat stability.
强效抗结核药物异烟肼（INH）的毒性被认为是由含血红素的过氧化氢酶介导的，该酶由结核分枝杆菌的katG基因编码。通过使用基于聚合酶链反应和单链构象多态性分析（PCR-SSCP）的新策略研究一组耐INH的临床分离株，以检测katG中的突变，从而获得了令人信服的证据。在大多数情况下，INH耐药性与错义突变有关，而在少数菌株中，该基因已被完全或部分删除。错义突变分为两组，其中较大的一组包含几个独立的突变，这些突变影响了该蛋白的N端过氧化物酶结构域，导致产生一种过氧化氢酶过氧化物酶，其酶活性大大降低且热稳定性增加。这些取代的影响可以通过以酵母相关酶细胞色素c过氧化物酶的晶体结构为模板的分子建模来解释。第二组包括一个频繁出现的氨基酸取代和一个单一突变，它们都位于C端结构域，但对酶活性或热稳定性均无明显影响。
