title: The adenosine deaminases of Plasmodium vivax and Plasmodium falciparum exhibit surprising differences in ligand specificity.
abstract: 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.
authors.affiliation: Emory University School of Medicine, Department of Biochemistry, Center for Fundamental and Applied Molecular Evolution, 1510 Clifton Road NE, Atlanta, GA 30322, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Ivanov
authors.forename: Ichiro
authors.initials: I
authors.lastname: Matsumura
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000737:chemistry; D000243:Adenosine Deaminase / Q000737:chemistry* / Q000235:genetics; D058892:Adenosine Deaminase Inhibitors / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D003198:Computer Simulation; D015195:Drug Design; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010963:Plasmodium falciparum / Q000201:enzymology*; D010966:Plasmodium vivax / Q000201:enzymology*; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics; D013045:Species Specificity; D040681:Structural Homology, Protein
chemical_list: D058892:Adenosine Deaminase Inhibitors; D015800:Protozoan Proteins; C010192:9-(2-hydroxy-3-nonyl)adenine; D000243:Adenosine Deaminase; D000225:Adenine