The hydrolase LpqI primes mycobacterial peptidoglycan recycling

Abstract

Growth and division by most bacteria requires remodelling and cleavage of their cell wall. A byproduct of this process is the generation of free peptidoglycan (PG) fragments known as muropeptides, which are recycled in many model organisms. Bacteria and hosts can harness the unique nature of muropeptides as a signal for cell wall damage and infection, respectively. Despite this critical role for muropeptides, it has long been thought that pathogenic mycobacteria such as Mycobacterium tuberculosis do not recycle their PG. Herein we show that M. tuberculosis and Mycobacterium bovis BCG are able to recycle components of their PG. We demonstrate that the core mycobacterial gene lpqI , encodes an authentic NagZ β- N -acetylglucosaminidase and that it is essential for PG-derived amino sugar recycling via an unusual pathway. Together these data provide a critical first step in understanding how mycobacteria recycle their peptidoglycan.

ActS activates peptidoglycan amidases during outer membrane stress in Escherichia coli

“…PG sacculi were isolated from E. coli Top10 as described previously (Glauner et al, 1988). The purified sacculi were subsequently labeled with fluorescein isothiocyanate (FITC) as described in (Moynihan et al, 2019). Briefly, 25 mg of PG was incubated with 12.5 mg of FITC in 3 ml 0.5 M sodium bicarbonate buffer pH 9.3.…”

Transporters Involved in the Biogenesis and Functionalization of the Mycobacterial Cell Envelope

“…Interestingly, LpqI works as an exoacting enzyme rather than an autolytic β-N-acetylglucosaminidase. 332 Finally, an arabinanase activity has been reported in the cell walls of M. smegmatis and Mtb and extensively exploited in the structural characterization of AG and LAM, but the corresponding enzyme remains to be identified. 335−337 Potential candidates for this function may reside in the as yet orphan GHs of Mtb identified by van Wyk et al 331 Upon their release from cell envelope glycoconjugates, the processes by which carbohydrates may re-enter the cytoplasm to participate in a new biosynthetic cycle remains poorly understood.…”

Evolution of Phosphorylases from N-Acetylglucosaminide Hydrolases in Family GH3

“…The true distinction between GHs and GPs in this family remains unknown, so it has become a common practice to measure how the presence of phosphate affects enzymatic activity whenever a new putative hexosaminidase is characterized. 14,15 We set out to take a closer look at the enigmatic glycosidases and phosphorylases in family GH3 to clear up the confusion surrounding the determinants of their activity and to examine whether a comparison of these enzymes can provide insights into how biotechnologically relevant phosphorylase activity can be established in the active site of conventional hydrolases.…”

“…They characterized a GH3 enzyme from Herbaspirillium seropedicae that shows regular N -acetylglucosaminidase activity, despite bearing that particular catalytic histidine. The true distinction between GHs and GPs in this family remains unknown, so it has become a common practice to measure how the presence of phosphate affects enzymatic activity whenever a new putative hexosaminidase is characterized. , …”