Mycobacterium tuberculosis mycolic acid synthesis machinery

The Mycobacterium tuberculosis mycolic acid synthesis machinery is a complex, multi-enzyme system responsible for the biosynthesis of mycolic acids, which are essential long-chain fatty acids that form the primary structural and protective component of the mycobacterial cell wall [1, 3]. This machinery consists of two distinct fatty acid synthase systems: FAS-I, which produces short-chain fatty acid precursors, and FAS-II, a dissociated system that elongates these precursors into long meromycolic chains [3, 7]. Key enzymes within this pathway, including the enoyl-ACP reductase InhA, the beta-ketoacyl-ACP synthases KasA and KasB, and the dehydratase complex HadABC, are vital for maintaining the cell envelope's impermeability and the bacterium's overall virulence [4, 11]. By creating a dense, waxy barrier, mycolic acids protect the pathogen from host immune defenses and many standard antibiotics [7, 10]. This machinery is the target of several frontline and second-line antitubercular drugs, such as isoniazid and ethionamide, which inhibit InhA to disrupt cell wall assembly and induce bacterial death [1, 9]. Given its essentiality for survival and the rise of drug-resistant strains, the mycolic acid synthesis machinery remains a critical focus for the development of novel antimicrobial therapies [5, 6].

Other names

Mycolic acid biosynthetic pathwayMycobacterial fatty acid synthase systemFAS-II complexMeromycolic acid synthesis machineryMycolic acid synthesis system

Inhibition of specific enzymes and transporters within the mycolic acid biosynthetic pathway, such as InhA (enoyl-ACP reductase), KasA/B (beta-ketoacyl-ACP synthases), HadABC (beta-hydroxyacyl-ACP dehydratases), and MmpL3 (transporter), which prevents the synthesis, elongation, and transport of mycolic acids, leading to cell wall instability and bacterial lysis [1, 4, 9].