Inhibition of hypoxanthine-guanine-xanthine phosphoribosyltransferase activity decreases the pool of 6-oxo and 6-amino purine nucleoside monophosphates required for DNA and RNA synthesis, resulting in a reduction in cell growth. Therefore, inhibitors of this enzyme have potential to control infections, caused by Plasmodium falciparum and Plasmodium vivax, Trypanosoma brucei, Mycobacterium tuberculosis, and Helicobacter pylori. Five compounds synthesized here that contain a purine base covalently linked by a prolinol group to one or two phosphonate groups have Ki values ranging from 3 nM to >10 μM, depending on the structure of the inhibitor and the biological origin of the enzyme. X-ray crystal structures show that, on binding, these prolinol-containing inhibitors stimulated the movement of active site loops in the enzyme. Against TBr in cell culture, a prodrug exhibited an EC50 of 10 μM. Thus, these compounds are excellent candidates for further development as drug leads against infectious diseases as well as being potential anticancer agents.

• MeSH
• Enzyme Inhibitors * pharmacology   chemistry   chemical synthesis   MeSH
• Catalytic Domain MeSH
• Crystallography, X-Ray MeSH
• Humans MeSH
• Models, Molecular MeSH
• Molecular Structure MeSH
• Pentosyltransferases * antagonists & inhibitors   metabolism   MeSH
• Drug Design * MeSH
• Trypanosoma brucei brucei drug effects   enzymology   MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• hypoxanthine-guanine-xanthine phosphoribosyltransferase MeSH Browser
• Enzyme Inhibitors * MeSH
• Pentosyltransferases * MeSH

Purine metabolism plays a ubiquitous role in the physiology of Mycobacterium tuberculosis and other mycobacteria. The purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is essential for M. tuberculosis growth in vitro; however, its precise role in M. tuberculosis physiology is unclear. Membrane-permeable prodrugs of specifically designed HGPRT inhibitors arrest the growth of M. tuberculosis and represent potential new antituberculosis compounds. Here, we investigated the purine salvage pathway in the model organism Mycobacterium smegmatis Using genomic deletion analysis, we confirmed that HGPRT is the only guanine and hypoxanthine salvage enzyme in M. smegmatis but is not required for in vitro growth of this mycobacterium or survival under long-term stationary-phase conditions. We also found that prodrugs of M. tuberculosis HGPRT inhibitors displayed an unexpected antimicrobial activity against M. smegmatis that is independent of HGPRT. Our data point to a different mode of mechanism of action for these inhibitors than was originally proposed.IMPORTANCE Purine bases, released by the hydrolytic and phosphorolytic degradation of nucleic acids and nucleotides, can be salvaged and recycled. The hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which catalyzes the formation of guanosine-5'-monophosphate from guanine and inosine-5'-monophosphate from hypoxanthine, represents a potential target for specific inhibitor development. Deletion of the HGPRT gene (Δhgprt) in the model organism Mycobacterium smegmatis confirmed that this enzyme is not essential for M. smegmatis growth. Prodrugs of acyclic nucleoside phosphonates (ANPs), originally designed against HGPRT from Mycobacterium tuberculosis, displayed anti-M. smegmatis activities comparable to those obtained for M. tuberculosis but also inhibited the ΔhgprtM. smegmatis strain. These results confirmed that ANPs act in M. smegmatis by a mechanism independent of HGPRT.

• Keywords
• Mycobacterium smegmatis, guanine, hypoxanthine, hypoxanthine-guanine phosphoribosyltransferase, inhibitors, purine salvage pathway,
• MeSH
• Antitubercular Agents chemistry   pharmacology   MeSH
• Hypoxanthine Phosphoribosyltransferase antagonists & inhibitors   chemistry   genetics   metabolism   MeSH
• Enzyme Inhibitors chemistry   pharmacology   MeSH
• Catalysis MeSH
• Metabolic Networks and Pathways MeSH
• Microbial Viability MeSH
• Mycobacterium smegmatis genetics   growth & development   metabolism   MeSH
• Plasmids genetics   MeSH
• Purines metabolism   MeSH
• Dose-Response Relationship, Drug MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antitubercular Agents MeSH
• Hypoxanthine Phosphoribosyltransferase MeSH
• Enzyme Inhibitors MeSH
• purine MeSH Browser
• Purines MeSH