Phosphate Binding in PNP Alters Transition-State Analogue Affinity and Subunit Cooperativity.

Purine nucleoside phosphorylases (PNPs) catalyze the phosphorolysis of 6-oxypurine nucleosides with an HPO dianion nucleophile. Nucleosides and phosphate occupy distinct pockets in the PNP active site. Evaluation of the HPO site by mutagenesis, cooperative binding studies, and thermodynamic and structural analysis demonstrate that alterations in the HPO binding site can render PNP inactive and significantly impact subunit cooperativity and binding to transition-state analogue inhibitors.

Cell-Effective Transition-State Analogue of Phenylethanolamine -Methyltransferase.

Phenylethanolamine -methyltransferase (PNMT) catalyzes the -adenosyl-l-methionine (SAM)-dependent methylation of norepinephrine to form epinephrine. Epinephrine is implicated in the regulation of blood pressure, respiration, Alzheimer's disease, and post-traumatic stress disorder (PTSD). Transition-state (TS) analogues bind their target enzymes orders of magnitude more tightly than their substrates.

Inhibition and Mechanism of Hypoxanthine-Guanine-Xanthine Phosphoribosyltransferase.

hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT) is essential for purine salvage of hypoxanthine into parasite purine nucleotides. Transition state analogue inhibitors of HGXPRT are characterized by kinetic analysis, thermodynamic parameters, and X-ray crystal structures. Compound , 9-deazaguanine linked to an acyclic ribocation phosphonate mimic, shows a kinetic of 0.

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

Phosphate groups play essential roles in biological processes, including retention inside biological membranes. Phosphodiesters link nucleic acids, and the reversible transfer of phosphate groups is essential in energy metabolism and cell-signalling processes. Phosphorylated metabolic intermediates are known targets for metabolic and disease-related disorders, and the enzymes involved in these pathways recognize phosphate groups in their catalytic sites.

Kinetic Characterization and Inhibition of Hypoxanthine-Guanine Phosphoribosyltransferases.

Chagas disease, caused by the parasitic protozoan , affects over 8 million people worldwide. Current antiparasitic treatments for Chagas disease are ineffective in treating advanced, chronic stages of the disease, and are noted for their toxicity. Like most parasitic protozoa, is unable to synthesize purines , and relies on the salvage of preformed purines from the host.

A resistant mutant of Plasmodium falciparum purine nucleoside phosphorylase uses wild-type neighbors to maintain parasite survival.

Plasmodium falciparum purine nucleoside phosphorylase (PfPNP) catalyzes an essential step in purine salvage for parasite growth. 4'-Deaza-1'-Aza-2'-Deoxy-1'-(9-Methylene)-Immucillin-G (DADMe-ImmG) is a transition state analog inhibitor of this enzyme, and P. falciparum infections in an Aotus primate malaria model can be cleared by oral administration of DADMe-ImmG.

Mechanism of inhibition of botulinum neurotoxin type A light chain by two quinolinol compounds.

Quinolinol-based compounds are a promising starting point for discovery of effective inhibitors of the clostridial neurotoxin, botulinum neurotoxin type A light chain (BoNT/A LC). Insights into the mechanism of inhibition by quinolinol compounds facilitate interpretation of docking data and inhibitor optimization. In this study, a fluorogenic substrate of BoNT/A, SNAPtide, was used to study the mechanism by which two new quinolinol compounds, MSU58 and MSU84, with IC values of 3.