Department of Social and Applied Science, College of Industrial Technology, King Mongkut's University of Technology North Bangkok, Bangkok 10800, Thailand.
Org Biomol Chem. 2018 Aug 29;16(34):6239-6249. doi: 10.1039/c8ob01428k.
The folate pathway is a recognized intervention point for treating parasitic and bacterial infections in humans. However, the efficacy of treatments targeting dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) has reduced due to disease-related mutations. This has prompted interest in other enzyme targets on this clinically validated pathway, including 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK). A challenge in the design of molecules to target this enzyme is that the precise mechanism of the reaction and the role of the active site residues are not fully understood. In this study, we report the first theoretical analysis of the catalytic pathway of the natural substrate using hybrid quantum mechanical/molecular mechanical (QM/MM) methods. The reaction profiles associated with three proposed general bases have been investigated, as well as the profile for two mutant enzymes, namely R92A and R82A. We identified R92 as the general base in the wildtype reaction. The predicted barriers are in good agreement with the observed experimental kcat values obtained for wildtype and mutant proteins.
叶酸途径是治疗人类寄生虫和细菌感染的公认干预点。然而，由于疾病相关的突变，针对二氢喋呤合成酶（DHPS）和二氢叶酸还原酶（DHFR）的治疗效果已经降低。这促使人们对该临床验证途径上的其他酶靶标产生了兴趣，包括 6-羟甲基-7,8-二氢蝶呤焦磷酸激酶（HPPK）。设计针对该酶的分子的一个挑战是，反应的精确机制和活性位点残基的作用尚未完全了解。在这项研究中，我们使用混合量子力学/分子力学（QM/MM）方法报告了天然底物催化途径的首次理论分析。研究了与三种提出的通用碱相关的反应曲线，以及两种突变酶 R92A 和 R82A 的曲线。我们确定 R92 是野生型反应中的通用碱。预测的势垒与为野生型和突变蛋白获得的观察到的实验 kcat 值非常吻合。
