Structure and catalytic regulation of Plasmodium falciparum IMP specific nucleotidase

Abstract

Plasmodium falciparum (Pf) relies solely on the salvage pathway for its purine nucleotide requirements, making this pathway indispensable to the parasite. Purine nucleotide levels are regulated by anabolic processes and by nucleotidases that hydrolyse these metabolites into nucleosides. Certain apicomplexan parasites, including Pf, have an IMP-specific-nucleotidase 1 (ISN1). Here we show, by comprehensive substrate screening, that PfISN1 catalyzes the dephosphorylation of inosine monophosphate (IMP) and is allosterically activated by ATP. Crystal structures of tetrameric PfISN1 reveal complex rearrangements of domain organization tightly associated with catalysis. Immunofluorescence microscopy and expression of GFP-fused protein indicate cytosolic localization of PfISN1 and expression in asexual and gametocyte stages of the parasite. With earlier evidence on isn1 upregulation in female gametocytes, the structures reported in this study may contribute to initiate the design for possible transmission-blocking agents.

Stereo-Defined Acyclic Nucleoside Phosphonates are Selective and Potent Inhibitors of Parasite 6-Oxopurine Phosphoribosyltransferases

“…28. 13 6-Chloro-9-(pent-4-en-1-yl)-purine (7). In a 100 mL round-bottom flask, 6-chloropurine (3.1 g, 20 mmol) was suspended in dry DMF (50 mL) and NaH (0.96 g, 24 mmol, 60% suspension in mineral oil) was added.…”

“… − Thus, they depend on HG­(X)­PRT activity for the synthesis of both their 6-oxopurine and 6-aminopurine nucleoside monophosphates, although, in the case of Pf , it has been reported that AMP can also be transported from the host cell in some cases (Figure ). In contrast, Trypanosoma brucei ( Tbr ) has AK and APRT activity, and thus, adenine and adenosine are precursors for the 6-oxopurine and 6-aminopurine nucleoside monophosphates in this pathogen (Figure ). …”

“…It should be noted, however, that the prepared The transport of AMP across the Pf membrane has been suggested; 6 however, alternative reports suggest that this is open to question. 7 Created with BioRender.com Figure 3. Chemical structures and K i values of two pyrrolidine nucleoside bisphosphonates (PNBPs), where the nucleobase is hypoxanthine, without and with a hydroxy group in the linker, compounds I and II, respectively.…”

Kiss and spit metabolomics highlights the role of the host cN-II enzyme on purine metabolism during pathogen infection

“…cN-II enzymes are present not only in human cells but are also present in other eukaryote and prokaryote organisms. PfISN1 is the first 5' nucleotidase reported in Plasmodium falciparum, which is an IMP-specific nucleotidase that is allosterically activated by ATP (16). Also, a human ecto-nucleotidase has been reported to produce adenosine from AMP in the T. gondii infection context (54,55).…”

“…Purines must be fully dephosphorylated before they can be taken up and used by the parasite (7). Purine nucleotide levels are regulated by host nucleotidases that hydrolyze these nucleotides into nucleosides (16) which are then transported to the interior of the parasite (17). There are purine transporters inside the parasite membrane that transport purine nucleobases or nucleosides into the parasite cytosol (22).…”