Publications

• Scission of the lactyl ether bond of N-acetylmuramic acid by Escherichia coli 'etherase'.

  Jaeger T., Arsic M., Mayer C.

  The ubiquitous bacterial cell wall sugar N-acetylmuramic acid (MurNAc) carries a unique D-lactyl ether substituent at the C3 position. Recently, we proposed an etherase capable of cleaving this lactyl ether to be part of the novel bacterial MurNAc dissimilation pathway (Dahl, U., Jaeger, T., Nguye ... >> More

  The ubiquitous bacterial cell wall sugar N-acetylmuramic acid (MurNAc) carries a unique D-lactyl ether substituent at the C3 position. Recently, we proposed an etherase capable of cleaving this lactyl ether to be part of the novel bacterial MurNAc dissimilation pathway (Dahl, U., Jaeger, T., Nguyen, B. T., Sattler, J. M., Mayer, C. (2004) J. Bacteriol. 186, 2385-2392). Here, we report the identification of the first known MurNAc etherase. The encoding gene murQ is located at 55 min on the Escherichia coli chromosome adjacent to murP, the MurNAc-specific phosphotransferase system. A murQ deletion mutant could not grow on MurNAc as the sole source of carbon and energy but could be complemented by expressing murQ from a plasmid. The mutant had no obvious phenotype when grown on different carbon sources but accumulated MurNAc 6-phosphate at millimolar concentrations from externally supplied MurNAc. Purified MurQ-His6 fusion protein and extracts of cells expressing murQ both catalyze the cleavage of MurNAc 6-phosphate, with GlcNAc 6-phosphate and D-lactate being the primary products. The 18O label from enriched water is incorporated into the sugar molecule, showing that the C3-O bond is cleaved and reformed by the enzyme. Moreover, an intermediate was detected and identified as an unsaturated sugar molecule. Based on this observation, we suggested a lyase-type mechanism (beta-elimination/hydration) for the cleavage of the lactyl ether bond of MurNAc 6-phosphate. Close homologs of murQ were found on the chromosome of several bacteria, and amino acid sequence similarity with the N-terminal domain of human glucokinase-regulatory protein (GckR or GKRP) was recognized. << Less

  J. Biol. Chem. 280:30100-30106(2005) [PubMed] [EuropePMC]

• Mechanistic studies on N-acetylmuramic acid 6-phosphate hydrolase (MurQ): an etherase involved in peptidoglycan recycling.

  Hadi T., Dahl U., Mayer C., Tanner M.E.

  Peptidoglycan recycling is a process in which bacteria import cell wall degradation products and incorporate them back into either peptidoglycan biosynthesis or basic metabolic pathways. The enzyme MurQ is an N-acetylmuramic acid 6-phosphate (MurNAc 6-phosphate) hydrolase (or etherase) that hydrol ... >> More

  Peptidoglycan recycling is a process in which bacteria import cell wall degradation products and incorporate them back into either peptidoglycan biosynthesis or basic metabolic pathways. The enzyme MurQ is an N-acetylmuramic acid 6-phosphate (MurNAc 6-phosphate) hydrolase (or etherase) that hydrolyzes the lactyl side chain from MurNAc 6-phosphate and generates GlcNAc 6-phosphate. This study supports a mechanism involving the syn elimination of lactate to give an alpha,beta-unsaturated aldehyde with (E)-stereochemistry, followed by the syn addition of water to give product. The observation of both a kinetic isotope effect slowing the reaction of [2-(2)H]MurNAc 6-phosphate and the incorporation of solvent-derived deuterium into C2 of the product indicates that the C2-H bond is cleaved during catalysis. The observation that the solvent-derived (18)O isotope is incorporated into the C3 position of the product, but not the C1 position, provides evidence of the cleavage of the C3-O bond and argues against imine formation. The finding that 3-chloro-3-deoxy-GlcNAc 6-phosphate serves as an alternate substrate is also consistent with an elimination-addition mechanism. Upon extended incubations of MurQ with GlcNAc 6-phosphate, the alpha,beta-unsaturated aldehydic intermediate accumulates in solution, and (1)H NMR analysis indicates it exists as the ring-closed form of the (E)-alkene. A structural model is developed for the Escherichia coli MurQ and is compared to that of the structural homologue glucosamine-6-phosphate synthase. Putative active site acid/base residues are probed by mutagenesis, and Glu83 and Glu114 are found to be crucial for catalysis. The Glu83Ala mutant is essentially inactive as an etherase yet is capable of exchanging the C2 proton of substrate with solvent-derived deuterium. This suggests that Glu83 may function as the acidic residue that protonates the departing lactate. << Less

  Biochemistry 47:11547-11558(2008) [PubMed] [EuropePMC]

• MurQ etherase is required by Escherichia coli in order to metabolize anhydro-N-acetylmuramic acid obtained either from the environment or from its own cell wall.

  Uehara T., Suefuji K., Jaeger T., Mayer C., Park J.T.

  MurQ is an N-acetylmuramic acid-phosphate (MurNAc-P) etherase that converts MurNAc-P to N-acetylglucosamine-phosphate and is essential for growth on MurNAc as the sole source of carbon (T. Jaegar, M. Arsic, and C. Mayer, J. Biol. Chem. 280:30100-30106, 2005). Here we show that MurQ is the only Mur ... >> More

  MurQ is an N-acetylmuramic acid-phosphate (MurNAc-P) etherase that converts MurNAc-P to N-acetylglucosamine-phosphate and is essential for growth on MurNAc as the sole source of carbon (T. Jaegar, M. Arsic, and C. Mayer, J. Biol. Chem. 280:30100-30106, 2005). Here we show that MurQ is the only MurNAc-P etherase in Escherichia coli and that MurQ and AnmK kinase are required for utilization of anhydro-MurNAc derived either from cell wall murein or imported from the medium. << Less

  J. Bacteriol. 188:1660-1662(2006) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Recycling of the anhydro-N-acetylmuramic acid derived from cell wall murein involves a two-step conversion to N-acetylglucosamine-phosphate.

  Uehara T., Suefuji K., Valbuena N., Meehan B., Donegan M., Park J.T.

  Escherichia coli breaks down over 60% of the murein of its side wall and reuses the component amino acids to synthesize about 25% of the cell wall for the next generation. The amino sugars of the murein are also efficiently recycled. Here we show that the 1,6-anhydro-N-acetylmuramic acid (anhMurNA ... >> More

  Escherichia coli breaks down over 60% of the murein of its side wall and reuses the component amino acids to synthesize about 25% of the cell wall for the next generation. The amino sugars of the murein are also efficiently recycled. Here we show that the 1,6-anhydro-N-acetylmuramic acid (anhMurNAc) is returned to the biosynthetic pathway by conversion to N-acetylglucosamine-phosphate (GlcNAc-P). The sugar is first phosphorylated by anhydro-N-acetylmuramic acid kinase (AnmK), yielding MurNAc-P, and this is followed by action of an etherase which cleaves the bond between D-lactic acid and the N-acetylglucosamine moiety of MurNAc-P, yielding GlcNAc-P. The kinase gene has been identified by a reverse genetics method. The enzyme was overexpressed, purified, and characterized. The cell extract of an anmK deletion mutant totally lacked activity on anhMurNAc. Surprisingly, in the anmK mutant, anhMurNAc did not accumulate in the cytoplasm but instead was found in the medium, indicating that there was rapid efflux of free anhMurNAc. << Less

  J. Bacteriol. 187:3643-3649(2005) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.