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Figure 1 | BMC Structural Biology

Figure 1

From: Conservation of structure and activity in Plasmodium purine nucleoside phosphorylases

Figure 1

Catalysis by PNP. Schematic diagrams showing the chemical reactions catalysed by PNP: (a) phosphorolysis, and (b) arsenolysis. These diagrams are based on arsenolytic/hydrolysis transition-state structures of PNPs [17, 3, 4]. Note protonation at N7, leading to formation of a positive charge, and glycosidic-bond cleavage resulting in formation of a ribo-oxocarbenium ion and negative charge in the purine ring at the transition state. This process occurs prior to nucleophilic attack as the catalytic reaction of PNP follows a SN1 type mechanism. (c) shows the transition state mimc inhibitor, Immucillin H (ImmH).

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