title: TheN-Acetylmuramic Acid 6-Phosphate Phosphatase MupP Completes thePseudomonasPeptidoglycan Recycling Pathway Leading to Intrinsic Fosfomycin Resistance.
abstract: Bacterial cells are encased in and stabilized by a netlike peptidoglycan (PGN) cell wall that undergoes turnover during bacterial growth. PGN turnover fragments are frequently salvaged by the cells via a pathway referred to as PGN recycling. Two different routes for the recycling of the cell wall sugarN-acetylmuramic acid (MurNAc) have been recognized in bacteria. InEscherichia coliand related enterobacteria, as well as in most Gram-positive bacteria, MurNAc is recovered via a catabolic route requiring a MurNAc 6-phosphate etherase (MurQ inE. coli) enzyme. However, many Gram-negative bacteria, includingPseudomonasspecies, lack a MurQ ortholog and use an alternative, anabolic recycling route that bypasses thede novobiosynthesis of uridyldiphosphate (UDP)-MurNAc, the first committed precursor of PGN. Bacteria featuring the latter pathway become intrinsically resistant to the antibiotic fosfomycin, which targets thede novobiosynthesis of UDP-MurNAc. We report here the identification and characterization of a phosphatase enzyme, named MupP, that had been predicted to complete the anabolic recycling pathway ofPseudomonasspecies but has remained unknown so far. It belongs to the large haloacid dehalogenase family of phosphatases and specifically converts MurNAc 6-phosphate to MurNAc. A ΔmupPmutant ofPseudomonas putidawas highly susceptible to fosfomycin, accumulated large amounts of MurNAc 6-phosphate, and showed lower levels of UDP-MurNAc than wild-type cells, altogether consistent with a role for MupP in the anabolic PGN recycling route and as a determinant of intrinsic resistance to fosfomycin.IMPORTANCEMany Gram-negative bacteria, but notE. coli, make use of a cell wall salvage pathway that contributes to the pool of UDP-MurNAc, the first committed precursor of cell wall synthesis in bacteria. This salvage pathway is of particular interest because it confers intrinsic resistance to the antibiotic fosfomycin, which blocksde novoUDP-MurNAc biosynthesis. Here we identified and characterized a previously missing enzyme within the salvage pathway, the MurNAc 6-phosphate phosphatase MupP ofP. putidaMupP, together with the other enzymes of the anabolic recycling pathway, AnmK, AmgK, and MurU, yields UDP-MurNAc, renders bacteria intrinsically resistant to fosfomycin, and thus may serve as a novel drug target for antimicrobial therapy.
authors.affiliation: Microbiology/Biotechnology, Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Borisova
authors.affiliation: Microbiology/Biotechnology, Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gisin
authors.affiliation: Microbiology/Biotechnology, Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany christoph.mayer@uni-tuebingen.de.
authors.forename: Christoph
authors.identifier: 0000-0003-4731-4851
authors.initials: C
authors.lastname: Mayer
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005578:Fosfomycin / Q000494:pharmacology*; D017353:Gene Deletion; D009112:Muramic Acids / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D016958:Pseudomonas putida / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009112:Muramic Acids; D010457:Peptidoglycan; C031651:N-acetylmuramic acid; D005578:Fosfomycin; C000621163:MupP protein, Pseudomonas putida; D010744:Phosphoric Monoester Hydrolases