Deciphering the Nature of Enzymatic Modifications of Bacterial Cell Walls

Abstract

The major constituent of bacterial cell wall is peptidoglycan, which in its crosslinked form is a polymer of considerable complexity that encases the entire bacterium. A functional cell wall is indispensable for the survival of the organism. There are several dozens of enzymes that assemble and disassemble the peptidoglycan dynamically within each bacterial generation. Understanding of the nature of these transformations is critical knowledge on these events. Octasaccharide peptidoglycans were prepared and studied with seven recombinant cell-wall-active enzymes (SltB1, MltB, RlpA, mutanolysin, AmpDh2, AmpDh3 and PBP5). With the use of highly sensitive mass spectrometry methods, we describe the breadth of reactions that these enzymes catalyze with the peptidoglycan and shed light on the nature of the cell-wall alteration performed by these enzymes. The enzymes exhibit broadly distinct preferences for their substrate peptidoglycans in the reactions that they catalyze.

Cell-Wall Recycling of the Gram-Negative Bacteria and the Nexus to Antibiotic Resistance

“…87 AmpD is a zinc-dependent endopeptidase that cleaves the amide link between the lactyl moiety of the MurNAc saccharide and the first l -Ala amino acid of the stem. 88,89,90–98 The peptide segments released from the stem by AmpD are reused as substrates by the Mpl ligase, 99–101 that transforms UDP-GlcNAc to UDP-MurNAc-tripeptide. The stemless anhMurNAc product of AmpD is transformed by AnmK-catalyzed ATP-dependent ring opening of the anhydrous saccharide structure, to give MurNAc-6-phosphate.…”

“…aeruginosa, for the ultimate purpose of inducing an inflammatory response in the host inflammation . AmpD is a zinc-dependent endopeptidase that cleaves the amide link between the lactyl moiety of the MurNAc saccharide and the first l -Ala amino acid of the stem. ,,− The peptide segments released from the stem by AmpD are reused as substrates by the Mpl ligase, − that transforms UDP-GlcNAc to UDP-MurNAc-tripeptide. The stemless anhMurNAc product of AmpD is transformed by AnmK-catalyzed ATP-dependent ring opening of the anhydrous saccharide structure, to give MurNAc-6-phosphate. , The mechanism of this enzyme is open to speculation. , There is no evidence supporting the organization of the first three of these four enzymes as an ordered pathway.…”

Structural basis of denuded glycan recognition by SPOR domains in bacterial cell division

“…RlpA septal ring localization has been shown in E. coli 12,13 and in P. aeruginosa 23 and its function is needed for efficient separation of daughter cells and maintenance of rod shape in P. aeruginosa 23 but not in E. coli 12,13 . RlpA exhibits a requirement for denuded glycan strands and a regulatory mechanism has been proposed in which amidases and RlpA work in tandem to degrade PG at the septum in division 23,27,28 (Fig. 1c).…”

Size‐Controlled Synthesis of β(1→4)‐GlcNAc Oligosaccharides Using an Endo‐Glycosynthase

“…Chemical syntheses of PG octasaccharides were only reported by Fukase and Fujimoto's group [20] as well as Mobashery's group. [21] Total syntheses of COs [22] are more documented, however the numerous steps impede the access to long-chain oligomers. Most publications indeed report the access to tetra-or hexasaccharides and to the best of our knowledge, the preparation of chitosan dodecasaccharide by Kuyama et al in 1993 [23] remained an isolated success until the efficient synthesis of a biotin-tagged heptasaccharide reported recently by Nifantiev's group.…”

“…Very few examples of synthetic PG oligosaccharides have been reported in the literature so far. Chemical syntheses of PG octasaccharides were only reported by Fukase and Fujimoto's group [20] as well as Mobashery's group [21] . Total syntheses of COs [22] are more documented, however the numerous steps impede the access to long‐chain oligomers.…”