The design of protozoan phosphoribosyltransferase inhibitors containing non-charged phosphate mimic residues

Gai, Sinan; Suthagar, Kajitha; Shaffer, Karl J.; Jiao, Wanting; Minnow, Yacoba V.T.; Glockzin, Kayla; Maatouk, Sean W.; Katzfuss, Ardala; Meek, Thomas D.; Schramm, Vern L.; Tyler, Peter C.

doi:10.1016/j.bmc.2022.117038

Cited by 1 publication

(3 citation statements)

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“…The striking conservation among the most potent inhibitors of Pf HGXPRT and TcHGPRT (although not in the same magnitude of potency) has been previously shown and discussed. 43,79 Both enzymes show high preference for Hxbased TSAIs (Hx being their preferred substrate), except for compound 1 (Gua-based), while Xan-based compounds showed lower inhibitory activity, as expected due to their active site composition at positions corresponding to residues 198, 204, and 205. In contrast, TcHGXPRT shows a remarkable preference for Xan as a substrate (Table 1), and such a property is reflected in the potent inhibition observed for compounds 5 (K i = 0.9 μM) and 10 (K i = 0.2 μM).…”

Section: Biochemistrymentioning

confidence: 82%

“…Concentration–response data was fit to eq , and K i values were calculated using eq . b Glockzin et al, 2022 c Gai et al, 2022 …”

Section: Resultsmentioning

confidence: 99%

“…The structures of Pf HGXPRT and Tc HG(X)PRTs, as well as of other Type I PRTases, ,, all show the extensive conservation in binding of both the purine and 5′-phosphate moieties of substrates, products, and NMP-based inhibitors. The location of the 5′-phosphate binding site, at the hinge of loop 2, may present challenges for the optimization of more soluble phosphate-mimic substituents, as we recently demonstrated; therefore, modifications in the purine ring and sugar moiety may hold the key to increased potency and selectivity against all T . cruzi isoforms.…”

Section: Discussionmentioning

confidence: 99%

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Kinetic and Structural Characterization of Trypanosoma cruzi Hypoxanthine–Guanine–Xanthine Phosphoribosyltransferases and Repurposing of Transition-State Analogue Inhibitors

Glockzin,

Meneely,

Hughes

et al. 2023

Biochemistry

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Over 70 million people are currently at risk of developing Chagas Disease (CD) infection, with more than 8 million people already infected worldwide. Current treatments are limited and innovative therapies are required. Trypanosoma cruzi, the etiological agent of CD, is a purine auxotroph that relies on phosphoribosyltransferases to salvage purine bases from their hosts for the formation of purine nucleoside monophosphates. Hypoxanthine–guanine–xanthine phosphoribosyltransferases (HGXPRTs) catalyze the salvage of 6-oxopurines and are promising targets for the treatment of CD. HGXPRTs catalyze the formation of inosine, guanosine, and xanthosine monophosphates from 5-phospho-d-ribose 1-pyrophosphate and the nucleobases hypoxanthine, guanine, and xanthine, respectively. T. cruzi possesses four HG(X)PRT isoforms. We previously reported the kinetic characterization and inhibition of two isoforms, TcHGPRTs, demonstrating their catalytic equivalence. Here, we characterize the two remaining isoforms, revealing nearly identical HGXPRT activities in vitro and identifying for the first time T. cruzi enzymes with XPRT activity, clarifying their previous annotation. TcHGXPRT follows an ordered kinetic mechanism with a postchemistry event as the rate-limiting step(s) of catalysis. Its crystallographic structures reveal implications for catalysis and substrate specificity. A set of transition-state analogue inhibitors (TSAIs) initially developed to target the malarial orthologue were re-evaluated, with the most potent compound binding to TcHGXPRT with nanomolar affinity, validating the repurposing of TSAIs to expedite the discovery of lead compounds against orthologous enzymes. We identified mechanistic and structural features that can be exploited in the optimization of inhibitors effective against TcHGPRT and TcHGXPRT concomitantly, which is an important feature when targeting essential enzymes with overlapping activities.

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Section: Biochemistrymentioning

confidence: 82%

“…Concentration–response data was fit to eq , and K i values were calculated using eq . b Glockzin et al, 2022 c Gai et al, 2022 …”

Section: Resultsmentioning

confidence: 99%