Mycobacteria express enzymes from both the de novo and purine-salvage pathways. However, the regulation of these processes and the roles of individual metabolic enzymes have not been sufficiently detailed. Both Mycobacterium tuberculosis (Mtb) and Mycobacterium smegmatis (Msm) possess three guaB genes, but information is only available on guaB2, which encodes an essential inosine 5'-monophosphate dehydrogenase (IMPDH) involved in de novo purine biosynthesis. This study shows that guaB1, annotated in databases as a putative IMPDH, encodes a guanosine 5'-monophosphate reductase (GMPR), which recycles guanosine monophosphate to inosine monophosphate within the purine-salvage pathway and contains a cystathionine-β-synthase domain (CBS), which is essential for enzyme activity. GMPR activity is allosterically regulated by the ATP/GTP ratio in a pH-dependent manner. Bioinformatic analysis has indicated the presence of GMPRs containing CBS domains across the entire Actinobacteria phylum.

• Klíčová slova
• CBS domain, GMPR, Mycobacterium, guaB1, purine biosynthesis,
• MeSH
• adenosintrifosfát MeSH
• cystathionin-beta-synthasa genetika   MeSH
• cystathionin * MeSH
• GMP-reduktasa genetika   metabolismus   MeSH
• guanosintrifosfát MeSH
• IMP-dehydrogenasa genetika   metabolismus   MeSH
• inosin MeSH
• inosinmonofosfát metabolismus   MeSH
• kyselina 5'-guanylová metabolismus   MeSH
• Mycobacterium tuberculosis * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenosintrifosfát MeSH
• cystathionin-beta-synthasa MeSH
• cystathionin * MeSH
• GMP-reduktasa MeSH
• guanosintrifosfát MeSH
• IMP-dehydrogenasa MeSH
• inosin MeSH
• inosinmonofosfát MeSH
• kyselina 5'-guanylová 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.

• Klíčová slova
• Mycobacterium smegmatis, guanine, hypoxanthine, hypoxanthine-guanine phosphoribosyltransferase, inhibitors, purine salvage pathway,
• MeSH
• antituberkulotika chemie   farmakologie   MeSH
• hypoxanthinfosforibosyltransferasa antagonisté a inhibitory   chemie   genetika   metabolismus   MeSH
• inhibitory enzymů chemie   farmakologie   MeSH
• katalýza MeSH
• metabolické sítě a dráhy MeSH
• mikrobiální viabilita MeSH
• Mycobacterium smegmatis genetika   růst a vývoj   metabolismus   MeSH
• plazmidy genetika   MeSH
• puriny metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antituberkulotika MeSH
• hypoxanthinfosforibosyltransferasa MeSH
• inhibitory enzymů MeSH
• purine MeSH Prohlížeč
• puriny MeSH