Emory University School of Medicine, Department of Biochemistry, Center for Fundamental and Applied Molecular Evolution, 1510 Clifton Road NE, Atlanta, GA 30322, USA.
J Mol Graph Model. 2012 May;35:43-8. doi: 10.1016/j.jmgm.2012.02.004. Epub 2012 Feb 28.
Plasmodium vivax and Plasmodium falciparum cause malaria, so proteins essential for their survival in vivo are potential anti-malarial drug targets. Adenosine deaminases (ADA) catalyze the irreversible conversion of adenosine into inosine, and play a critical role in the purine salvage pathways of Plasmodia and their mammalian hosts. Currently, the number of selective inhibitors of Plasmodium ADAs is limited. One potent and widely used inhibitor of the human ADA (hADA), erythro-9-(2-hydroxy-3-nonly)adenine (EHNA), is a very weak inhibitor (K(i)=120 μM) of P. falciparum ADA (pfADA). EHNA-like compounds are thus excluded from consideration as potential inhibitors of Plasmodium ADA in general. However, EHNA activity in P. vivax ADA (pvADA) has not been reported. Here we applied computational molecular modeling to identify ligand recognition mechanisms unique to P. vivax and P. falciparum ADA. Our biochemical experiments show that EHNA is at least 60-fold more potent against pvADA (K(i)=1.9 μM) than against pfADA. The D172A pvADA mutant is bound even more tightly (K(i)=0.9 μM). These results improve our understanding of the mechanisms of ADA ligand recognition and species-selectivity, and facilitate the rational design of novel EHNA-based ADA inhibitors as anti-malarial drugs. To demonstrate a practical application of our findings we have computationally predicted a novel potential inhibitor of pvADA that will not interact with the human ADA.
疟原虫 vivax 和疟原虫 falciparum 引起疟疾，因此，对其在体内生存至关重要的蛋白质是潜在的抗疟药物靶点。腺苷脱氨酶 (ADA) 催化腺苷不可逆转化为肌苷，在疟原虫及其哺乳动物宿主的嘌呤补救途径中发挥关键作用。目前，对疟原虫 ADA 的选择性抑制剂数量有限。一种有效的、广泛使用的人 ADA (hADA) 抑制剂——赤式-9-(2-羟基-3-壬基)腺嘌呤 (EHNA)，对疟原虫 falciparum ADA (pfADA) 的抑制作用非常弱 (K(i)=120 μM)。因此，EHNA 类似物不能作为一般的疟原虫 ADA 潜在抑制剂来考虑。然而，EHNA 在 vivax 疟原虫 ADA (pvADA) 中的活性尚未报道。在这里，我们应用计算分子建模来鉴定疟原虫 vivax 和疟原虫 falciparum ADA 特有的配体识别机制。我们的生化实验表明，EHNA 对 pvADA (K(i)=1.9 μM) 的抑制作用至少比 pfADA 强 60 倍。D172A pvADA 突变体的结合更紧密 (K(i)=0.9 μM)。这些结果提高了我们对 ADA 配体识别和物种选择性机制的理解，并促进了基于 EHNA 的新型 ADA 抑制剂作为抗疟药物的合理设计。为了证明我们发现的实际应用，我们通过计算预测了一种新型潜在的 pvADA 抑制剂，它不会与人类 ADA 相互作用。
