Structural determinants of the oxidative stress response

提出的研究的主要目标是表征保护生物体免受氧化应激的蛋白质。20多年来，Loewen实验室的研究一直集中在单功能过氧化氢酶和双功能过氧化氢酶-过氧化物酶上，它们的主要生理作用是将潜在有毒的过氧化氢降解为无害的水和氧气。工作已经从细菌遗传分析，通过分子遗传表征到蛋白质结构测定，并大大提高了对酶在不同生物体中如何应对生理挑战的理解。最近在实验室中采用的蛋白质x射线晶体学程序使得解决有关酶中催化机制的问题成为可能；拟议的研究将继续朝这个方向进行。提出的研究目标是表征保护生物体免受过氧化氢侵害的因素，具体目标是表征和合理化影响过氧化氢酶-过氧化物酶和单功能过氧化氢酶催化机制的结构特征。双功能过氧化氢酶-过氧化物酶因其作为广泛使用的抗结核前药异烟肼的激活剂而声名狼藉。特别是，缺乏这种酶的结核分枝杆菌菌株对该药物具有耐药性，从而成为耐异烟肼结核病传播的最常见原因，并产生严重的健康风险。拟议研究的一个分支将侧重于确定异烟肼活化的催化机制。这项研究将通过更好地理解过氧化氢降解和异烟肼活化作为抗结核病药物的机制，提高我们对酶催化的认识。

The primary goal of the proposed research is to characterize proteins that protect organisms against oxidative stress. For over 20 years, research in the Loewen laboratory has been focused on monofunctional catalases and bifunctional catalase-peroxidases which have as their main physiological role the degradation of potentially toxic hydrogen peroxide to harmless water and oxygen. Work has progressed from bacterial genetic analysis, through molecular genetic characterization to protein structure determination and has provided a greatly improved understanding of how the enzymes respond to physiological challenge in different organisms. The recent adoption of protein X-ray crystallography procedures in the laboratory has made it possible to address questions about the catalytic mechanisms operating in the enzymes; the proposed research will continue in this direction. The goal of the proposed research is to characterize factors that protect organisms against hydrogen peroxide and the specific objectives are to characterize and rationalize structural features that affect the catalytic mechanisms in catalase-peroxidases and monofunctional catalases. The bifunctional catalase-peroxidases have gained considerable notoriety from their role as the activator of the widely used anti-tubercular pro-drug isoniazid. In particular, strains of M. tuberculosis lacking the enzyme are resistant to the drug, giving rise to the most common cause of the spread of isoniazid-resistant tuberculosis and producing a serious health risk. One branch of the proposed research will focus on defining the catalytic mechanism involved in isoniazid activation. The research will enhance our knowledge of enzyme catalysis by providing a better understanding of the mechanisms of hydrogen peroxide degradation and of isoniazid activation as a drug against tuberculosis.