MSMEG_2432 of Mycobacterium smegmatis mc2155 is a dual function enzyme that exhibits DD-carboxypeptidase and β-lactamase activities.

MSMEG_2432 of Mycobacterium smegmatis mc2155 is a dual function enzyme that exhibits DD-carboxypeptidase and β-lactamase activities. Microbiology. 2020 Apr 17;: Authors: Pandey SD, Jain D, Kumar N, Adhikary A, Kumar N G, Ghosh AS Abstract Mycobacterial peptidoglycan (PG) is an unsolved puzzle due to its complex structure and involvement of multiple enzymes in the process of its remodelling. dd-Carboxypeptidases are low molecular mass penicillin-binding proteins (LMM-PBPs) that catalyzes the cleavage of terminal d-Ala of muramyl pentapeptide branches and thereby helps in the PG remodelling process. Here, we have assigned the function of a putative LMM-PBP, MSMEG_2432 of Mycobacterium smegmatis, by showing that it exhibits both dd-CPase and β-lactamase activities. Like conventional dd-CPase (PBP5 from E. coli), upon ectopic complementation in a deformed seven PBP deletion mutant of E. coli, MSMEG_2432 has manifested its ability to restore ~75 % of the cell population to their normal rod shape. Further, in vitrodd-CPase assay has confirmed its ability to release terminal d-Ala from the synthetic tripeptide and the peptidoglycan mimetic pentapeptide substrates ending with d-Ala-d-Ala. Also, elevated resistance against penicillins and cephalosporins upon ectopic expression of MSMEG_2432 suggests the presence of β-lactamase activity, which is further confirmed in vitro through nitrocefin hydrolysis assay. Moreover, it is found apparen...
Source: Microbiology - Category: Microbiology Authors: Tags: Microbiology Source Type: research