Purkan P, Ihsanawati I, Natalia D, Syah Y M, Retnoningrum D S, Siswanto I
Department of Chemistry, Faculty of Sciences and Technology, Airlangga University; Surabaya, Indonesia.
Biochemistry Research Division, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Bandung, Indonesia.
J Med Life. 2018 Apr-Jun;11(2):160-167.
Isoniazid (INH) is a drug for the treatment of tuberculosis in patients infected with Mycobacterium tuberculosis. The katG enzyme, or catalase-peroxidase, activates the pro-drug INH that is coded by the katG gene in M. tuberculosis. Mutations of the katG gene in M. tuberculosis are a major INH resistance mechanism. The M. tuberculosis clinical isolate R2 showed INH resistance at a high level of 10 µg/mL. However, the molecular basis for the resistance is unclear. The identification of a mutation in the katG gene of the clinical isolate R2 showed four mutations, i.e., C1061T, G1261 A, G1388T, G2161A, which correspond to the amino acid substitutions T354I, G421S, R463L, and V721M, respectively. The mutant katG gene, along with the wild-type were cloned, expressed and purified. The mutant enzyme showed 86.5% of catalase and 45% of peroxidase activities in comparison to the wild type. The substitutions of TI and GS in mutant katG R2 created significant instability in the adduct triad complex (Trp107-Tyr229-Met255), a part of the active site of the catalase-peroxidase enzyme in the model structure analysis. The events could be based on the high resistance of the clinical isolate R2 toward INH as the molecular basis.
异烟肼（INH）是一种用于治疗感染结核分枝杆菌患者结核病的药物。katG酶，即过氧化氢酶-过氧化物酶，可激活结核分枝杆菌中由katG基因编码的前体药物INH。结核分枝杆菌中katG基因的突变是主要的INH耐药机制。结核分枝杆菌临床分离株R2对INH的耐药水平高达10μg/mL。然而，耐药的分子基础尚不清楚。对临床分离株R2的katG基因进行突变鉴定，发现有四个突变，即C1061T、G1261A、G1388T、G2161A，分别对应氨基酸替代T354I、G421S、R463L和V721M。将突变型katG基因与野生型基因一起进行克隆、表达和纯化。与野生型相比，突变酶的过氧化氢酶活性为86.5%，过氧化物酶活性为45%。在模型结构分析中，突变型katG R2中的TI和GS替代在加合物三联体复合物（Trp107-Tyr229-Met255）中产生了显著的不稳定性，该复合物是过氧化氢酶-过氧化物酶活性位点的一部分。这些事件可能是临床分离株R2对INH高耐药性的分子基础。
