Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States.
Department of Chemistry and Physical Sciences, Pace University, 1 Pace Plaza, New York, New York 10038, United States.
Biochemistry. 2021 Nov 30;60(47):3582-3595. doi: 10.1021/acs.biochem.1c00470. Epub 2021 Nov 8.
Temperature adaptation is ubiquitous among all living organisms, yet the molecular basis for this process remains poorly understood. It can be assumed that for parasite-host systems, the same enzymes found in both organisms respond to the same selection factor (human body temperature) with similar structural changes. Herein, we report the existence of a reversible temperature-dependent structural transition for the glycolytic enzyme lactate dehydrogenase (LDH) from the malaria parasite (pfLDH) and human heart (hhLDH) occurring in the temperature range of human fever. This transition is observed for LDHs from psychrophiles, mesophiles, and moderate thermophiles in their operating temperature range. Thermodynamic analysis reveals unique thermodynamic signatures of the LDH-substrate complexes defining a specific temperature range to which human LDH is adapted and parasite LDH is not, despite their common mesophilic nature. The results of spectroscopic analysis combined with the available crystallographic data reveal the existence of an active center within pfLDH that imparts psychrophilic structural properties to the enzyme. This center consists of two pockets, one formed by the five amino acids (5AA insert) within the substrate specificity loop and the other by the active site, that mutually regulate one another in response to temperature and induce structural and functional changes in the Michaelis complex. Our findings pave the way toward a new strategy for malaria treatments and drug design using therapeutic agents that inactivate malarial LDH selectively at a specific temperature range of the cyclic malaria paroxysm.
温度适应在所有生物体中普遍存在，但这一过程的分子基础仍知之甚少。可以假设，对于寄生虫-宿主系统，两种生物体中发现的相同酶会对相同的选择因素（人体温度）产生相似的结构变化。在此，我们报告了疟原虫（pfLDH）和人心（hhLDH）糖酵解酶乳酸脱氢酶（LDH）存在可逆的温度依赖结构转变，该转变发生在人体发热的温度范围内。在其工作温度范围内，来自嗜冷菌、中温菌和中度嗜热菌的 LDH 都观察到这种转变。热力学分析揭示了 LDH-底物复合物的独特热力学特征，定义了一个特定的温度范围，人体 LDH 适应这个范围，而寄生虫 LDH 则不适应，尽管它们具有共同的嗜中性。光谱分析的结果与现有的晶体学数据相结合，揭示了 pfLDH 中存在一个活性中心，赋予了酶的低温结构特性。该中心由底物特异性环内的五个氨基酸（5AA 插入）形成的一个口袋和由活性位点形成的另一个口袋组成，它们相互调节，以响应温度并诱导米氏复合物的结构和功能变化。我们的发现为疟疾治疗和药物设计开辟了一条新途径，使用的治疗剂可以在周期性疟疾发作的特定温度范围内选择性地使疟原虫 LDH 失活。
