International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 09 | Sep 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2789 ELECTRON SINK AS A POTENTIAL DRUG TARGET: IN SILICO DRUG DEVELOPMENT AGAINST MYCOBACTERIUM TUBERCULOSIS Rojina Thapa 1 , Bhuwan Gurung 2 , Sudip Khadka 3 , Pramod Aryal 4 , Rameshwar Adhikari 5 1,2 Research Associates, National Fishery Research Centre, NARC, Godawari, Nepal 3 Student, Dept. of Biotechnology, SANN International College, Kathmandu, Nepal 4 Chief Scientist, Alpha Agro Pvt. Ltd., Birgunj, Nepal 5 Professor, Research Centre for Applied Science and Technology, Tribhuvan University, Kirtipur, Nepal ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - Latency of Mycobacterium tuberculosis and prolonged therapy regimen with emergence of MDR (multi- drug resistance) has mandated new therapy and it is prudent new antimicrobials be developed. Taking one of the potent mechanisms of actions of most of the antibiotics of generating reactive oxygen species (ROS) which the resistance bugs tend to mitigate in exhibiting resistance, one of the areas to develop antibiotics would be disruption of pathogens’ ROS evading mechanism and prevention of entry to low metabolic state. In this regard, glutathione and mycothiol, two electron sink thiols, biosynthetic pathway were chosen as target metabolic network. Based on Flux Balance Analysis (FBA) and OGEE (Online Gene Essentiality) results six proteins, MshA, MshC, CysM, CysK, MetH and Mrx-1, were taken as lead targets. NCI database II was taken as ligand database and top ten ligands with higher binding potential were screened for each proteins. They were further screened for ADME/T and druglikeness from which two ligands: ZINC16951320 and ZINC00990239 with higher binding energy towards all six enzymes as multi- drug target molecules were narrowed down. It is suggested that these molecules be further pursued for additional works on drug development as drug candidate leads and their antimicrobial potential be explored in other pathogens than Mycobacterium to develop novel antimicrobials that have broad spectrum. Key Words: MDR, ROS, electron sink thiols, multi-target drug, broad spectrum 1. INTRODUCTION The efficacy of antibiotics has been endangered by the rapid and widespread emergence of resistant bacterial strains towards therapeutics, forming a league of multi-drug resistant superbugs. And similar is the case in M. tuberculosis, a causative agent of (TB), which is already multidrug-resistant (MDR) [4]. In 2017, WHO marked TB as the ninth leading cause of death worldwide and the leading cause from a single infectious agent, ranking above HIV/AIDS. Metabolically diverse population of M. tuberculosis within the human host requiring 6–9 months of chemotherapy with a combination of frontline antibiotics, slow clearance rate[23], latent/persistent infection[22] make the TB treatment difficult. Besides M. tuberculosis strains, resistant to four or more of the front-line treatments i.e., extremely drug-resistant strains (XDR) have appeared and spread rapidly in the last decade or so [17]. And now there are TDR (totally drug resistant strains), compromising TB therapy throughout the world [20]. This rise in resistance has limited our repertoire of effective antimicrobials [8] which ensures the need for continual cycles of discovery and development of new antibiotics. The generation of reactive oxygen species (ROS) is the central and common mechanism of antibiotics mediated lethality in bacterial cell and mitigating this allows bacteria to develop resistance against the antibiotics. It is done through the augmentation of cellular respiration followed by Fenton catalyzed Haber-Weiss reaction [5]. Figure 1: Schematic of Hydroxyl radical hypothesis of antibiotic action [8] Sulfur assimilation pathway, particularly cysteine mediated through H2S production [11] and glutathione/mycothiol mediated electron sink [21], is found to be involved in antibiotics resistance through ROS mitigation. Genes involved in sulfur metabolism have consistently been identified as up-regulated in response to oxidative stress, nutrient starvation and dormancy adaptation and during macrophage infection [7]. Mycothiol is a principal low molecular thiol compound in actinobacteria, which acts as a redox buffer and is essential for the cellular defence against oxidative stress and antibiotics [12]. Hence, one of the areas for drug development could be impeding ROS mitigating mechanism.