Mycobacterium tuberculosis Emb arabinosyltransferases (Emb)

Mycobacterium tuberculosis Emb arabinosyltransferases (EmbA, EmbB, and EmbC) are essential membrane-associated enzymes involved in the biosynthesis of the mycobacterial cell wall (ResearchGate, https://www.researchgate.net/publication/26753831_EmbC_Is_an_Essential_Arabinosyltransferase_in_Mycobacterium_tuberculosis). These enzymes catalyze the polymerization of D-arabinofuranose into the arabinan segments of arabinogalactan (AG) and lipoarabinomannan (LAM), which are critical structural and functional components of the cell envelope (ASM, https://journals.asm.org/doi/10.1128/jb.00315-07). EmbA and EmbB are primarily responsible for the synthesis of the arabinan portion of AG, while EmbC is dedicated to LAM synthesis (NIH, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2737844/). These polysaccharides provide a robust permeability barrier that protects the bacterium from environmental stress and host immune responses. The Emb proteins are the primary therapeutic targets of ethambutol, a cornerstone first-line drug used in the treatment of tuberculosis (NIH, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8755434/). Ethambutol acts by inhibiting these arabinosyltransferases, thereby disrupting cell wall assembly and increasing the permeability of the cell envelope to other antitubercular agents (PatSnap, https://www.patsnap.com/resources/blog/ethambutol-hydrochloride-mechanism-of-action/). Resistance to ethambutol is a significant clinical challenge and is most commonly associated with mutations in the embB gene, particularly at codon 306 (Frontiers, https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.954414/full). Understanding the structure and function of these enzymes is vital for developing new treatments against drug-resistant strains of M. tuberculosis.

Other names

Arabinosyltransferase AArabinosyltransferase BArabinosyltransferase CEmbAEmbBEmbCRv3794Rv3795Rv3793EmbCAB operon

Ethambutol inhibits the Emb arabinosyltransferase enzymes, specifically blocking the polymerization of D-arabinofuranose into the arabinan components of the mycobacterial cell wall (NIH, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2737844/). This disruption prevents the assembly of the mycolyl-arabinogalactan-peptidoglycan complex, leading to increased cell wall permeability and bacteriostasis (BOC Sciences, https://www.bocsci.com/ethambutol-mechanism-of-action.html).