title: Characterization of an N-acetylmuramic acid/N-acetylglucosamine kinase of Clostridium acetobutylicum.
abstract: We report here the cloning and characterization of a cytoplasmic kinase of Clostridium acetobutylicum, named MurK (for murein sugar kinase). The enzyme has a unique specificity for both amino sugars of the bacterial cell wall, N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc), which are phosphorylated at the 6-hydroxyl group. Kinetic analyses revealed Km values of 190 and 127 μM for MurNAc and GlcNAc, respectively, and a kcat value (65.0 s(-1)) that was 1.5-fold higher for the latter substrate. Neither the non-N-acetylated forms of the cell wall sugars, i.e., glucosamine and/or muramic acid, nor epimeric hexoses or 1,6-anhydro-MurNAc were substrates for the enzyme. MurK displays low overall amino acid sequence identity (24%) with human GlcNAc kinase and is the first characterized bacterial representative of the BcrAD/BadFG-like ATPase family. We propose a role of MurK in the recovery of muropeptides during cell wall rescue in C. acetobutylicum. The kinase was applied for high-sensitive detection of the amino sugars in cell wall preparations by radioactive phosphorylation.
authors.affiliation: Fachbereich Biologie, Molekulare Mikrobiologie, Universität Konstanz, 78457 Constance, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Reith
authors.forename: Anne
authors.initials: A
authors.lastname: Berking
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayer
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D046969:Clostridium acetobutylicum / Q000201:enzymology* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009112:Muramic Acids / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D009112:Muramic Acids; C031651:N-acetylmuramic acid; D017853:Phosphotransferases (Alcohol Group Acceptor); C018716:N-acetylglucosamine kinase; D000117:Acetylglucosamine