The hydrolase LpqI primes mycobacterial peptidoglycan recycling

Abstract

30Growth and division by most bacteria requires remodeling and cleavage of their cell 31 wall. A byproduct of this process is the generation of free peptidoglycan (PG) fragments known 32 as muropeptides. These muropeptides are recycled in many model organisms, where the 33 bacteria can harness their unique nature as a signal for cell wall damage. These molecules also 34 serve as important signals for hosts where binding to specific receptors reports on the presence 35 of intracellular bacteria. Despite this critical role for muropeptides, it has long been thought that 36 pathogenic mycobacteria such as Mycobacterium tuberculosis do not recycle their PG. Herein 37 we show that M. tuberculosis and Mycobacterium bovis BCG are both able to recycle 38 components of their PG. We demonstrate that MurNAc but not GlcNAc can be metabolised by 39All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/312876 doi: bioRxiv preprint first posted online May. 3, 2018; 2 mycobacteria and that stem-peptide recycling proceeds independent of amino sugar recovery. 40In addition, we demonstrate that the core-mycobacterial gene lpqI encodes an authentic NagZ 41 β-N-acetylglucosaminidase, which is essential for recycling MurNAc. Surprisingly, loss of lpqI 42 leads to antimicrobial resistance and increased proliferation in macrophages. This supports a 43 model whereby the amount of PG released by mycobacterial cells is tightly controlled in order 44 to effectively modulate the infection process. 45

The endogenous galactofuranosidase GlfH1 hydrolyzes mycobacterial arabinogalactan

“…LpqI cleaves GlcpNAc-MurpNAc disaccharides, once its stem-peptide is removed, allowing the release of free MurpNAc. The MurpNAc is then followed by D-lactyl-ether cleavage to release lactate, which can be used by the cell under aerobic conditions (11). The highlight of these two mycobacterial enzymes, LpqI and GlfH1, allows us to progress in the understanding of the remodeling and the recycling of mycobacterial major cell envelope constituents.…”

Cell wall peptidoglycan inMycobacterium tuberculosis: An Achilles’ heel for the TB-causing pathogen

“…Recent work by Moynihan et al . provided evidence for the uptake of muropeptide fragments in M. tuberculosis and M. bovis BCG; where they show cleavage of stem peptide followed by disaccharide cleavage by LpqI (NagZ) and finally lactyl-ether removal from the Mur N Ac moiety (Moynihan et al 2019…”

Synthesis and recycling of the mycobacterial cell envelope

“…It has long been established that they promote resuscitation from dormancy, but recently they have also been shown to be involved in mycobacterial biofilm formation [ 29 ]. Following cleavage by the remodelling enzymes, there is limited release of the peptidoglycan fragments for immune system stimulation [ 4 •• ].…”

“…Developments in genomic and molecular techniques have enabled the majority of the structural elements and biosynthetic pathways of the Mtb cell wall to be resolved. The most recent evidence has revealed that mycobacteria have the machinery to recycle their cell envelope, opening up the possibility of discovering a plethora of undefined enzymes [ 4 •• , 5 , 6 ]. This review focuses on the current understanding of the structure, biosynthesis, remodelling and recycling of the mycobacterial cell envelope.…”