Identification validation and efficacy of combination of L D transpeptidase and D D transpeptidase inhibitors against Mycobacterium tuberculosis

Abstract

An effective treatment option for tuberculosis (TB) is inadequate. The current treatment regimen encompasses drugs targeting multiple targets involved in key cellular pathways in Mycobacterium tuberculosis. The present study investigates the anti-mycobacterial activity of a combination of Amoxicillin-Clavulanic acid (AMC) and a repurposed drug for the treatment of TB. By adopting a computational structure-based drug design approach, we repurposed Diosmin (DIO), by targeting the L,D-transpeptidase (Ldt) enzymes taking part in the cell wall biosynthesis in M. tuberculosis. newlineThe peptidoglycan (PG) of M. tuberculosis comprise two types of cross-linkages namely, classical and non-classical type mediated by D,D-transpeptidase and Ldt enzymes. Blocking these two enzymes simultaneously will inhibit the PG cross-linking leading to the cell wall lysis and bacterial death. The conventional and#946;-lactam drug, Amoxicillin is an inhibitor of D,D-transpeptidase enzyme. However, M. tuberculosis is innately resistant to Amoxicillin due to the production of and#946;-lactam degrading enzyme called and#946;-lactamase. A combination of Amoxicillin with a and#946;-lactamase inhibitor like Clavulanic acid can be used effectively to inhibit the formation of classical type PG cross-linking. In the present study, we propose a combination of drugs for the treatment of TB involving AMC and DIO by inhibiting the classical and non-classical cross-linkages respectively. newlineAfter oral administration of DIO, it rapidly gets converted into its aglycone form Diosmetin (DMT). Thus, DIO or DMT binding towards both the Ldt enzymes was studied using molecular docking, molecular dynamics simulation and bioassay techniques. The minimum bactericidal concentration of DIO (or DMT) and AMC combination was determined against Mycobacterium marinum. It is a widely used organism for studying the mycobacterial pathogenesis and it causes TB-like infection. The combination of AMC-DIO and AMC-DMT exhibited superior mycobactericidal activity as compared to individual drugs, ...