LipG a bifunctional phospholipase/thioesterase involved in mycobacterial envelope remodeling

Abstract

Tuberculosis caused by Mycobacterium tuberculosis is currently one of the leading causes of death from an infectious agent. The main difficulties encountered in eradicating this bacteria are mainly related to (i) a very complex lipid composition of the bacillus cell wall, (ii) its ability to hide from the immune system inside the granulomas, and (iii) the increasing number of resistant strains. In this context, we were interested in the Rv0646c (lipGMTB) gene located upstream to the mmaA cluster which is described as being crucial for the production of cell wall components and required for the bacilli adaptation and survival in mouse macrophages. Using biochemical experiments combined with the construction of deletion and overexpression mutant strains in Mycobacterium smegmatis, we found that LipGMTB is a cytoplasmic membrane-associated enzyme that displays both phospholipase and thioesterase activities. Overproduction of LipGMTB decreases the glycopeptidolipids (GPL) level concomitantly to an increase in phosphatidylinositol (PI) which is the precursor of the PI mannoside (PIM), an essential lipid component of the bacterial cell wall. Conversely, deletion of the lipGMS gene in M. smegmatis leads to an overproduction of GPL, and subsequently decreases the strain susceptibility to various antibiotics. All these findings demonstrate that LipG is involved in cell envelope biosynthesis/remodeling, and consequently this enzyme may thus play an important role in mycobacterial physiology.

Identification of potential lipid biomarkers for active pulmonary tuberculosis using ultra-high-performance liquid chromatography-tandem mass spectrometry

“…Interestingly, the results of this study were closely related to the degree of necrosis. Besides, some studies have demonstrated that the genome of M. tuberculosis has abundant genes encoding phospholipases, 29,30 suggesting that drugs can be developed to interfere with the expression of phospholipase gene to change the energy metabolism of M. tuberculosis 30 in order to block the destruction of host cells. However, the aforementioned enzymes are also of great abundance in the cells of the human body, and further studies are needed to find specific inhibitors for M. tuberculosis lipolytic enzymes.…”

The Chemistry and Biology of Cyclophostin, the Cyclipostins and Related Compounds

“…This suggests that there may be different modes of action with each set of compounds. Using activity-based protein profiling, 23 potential target enzymes of compound ( 28 ), which exhibited the best extracellular anti-tubercular activity, were identified [26,27,28,29,30]. Remarkably, all of the identified proteins were serine or cysteine enzymes; and most of them are involved in M. tb lipid metabolism or cell wall biosynthesis.…”

“…Mass spectroscopic and X-ray crystallographic studies with several different enzymes [21,22,26,27,28,29,30] have shown that the enolphosphates (and phosphonates) function by phosphorylation of the active site serine (Figure 5). In some cases, the inactivated enzyme undergoes further chemistry by loss of the β-ketoester moiety [28].…”

A competitive activity-based protein profiling platform yields cell wall synthesis inhibitors active against replicating and non-replicatingMycobacterium tuberculosis

“…Five overlapped (TesA, Rv1730c, LipC, LipM, AmiB2) with prioritized targets from our comparative analysis (Table 2), but the other six serine hydrolases were excluded due to a high degree of inhibition by AA702 (Rv0183, LipG, LipH, LipO, AmiC, Rv0293c). Four of these excluded targets-Rv0183, the phospholipase/thioesterase LipG (Santucci et al, 2018), the esterase LipH (Canaan et al, 2004), and the putative lipase LipO)-were also identified as direct targets of the alkyne-modified derivatives of lalistat, THL, or EZ120. Our comparison of AA692 and AA702 suggests that these enzymes are non-selectively targeted by active and inactive antibacterial compounds and that their inhibition may thus be unrelated to restricting Mtb growth or survival.…”