Mycolyltransferase 85B (Ag85B) (Ag85B)

Mycolyltransferase 85B, also known as Ag85B or FbpB, is a major secretory protein of Mycobacterium tuberculosis and a key enzyme in the biosynthesis of the mycobacterial cell wall [1]. It belongs to the Antigen 85 complex, which catalyzes the transfer of mycolic acids onto trehalose or the arabinogalactan layer, forming trehalose dimycolate (cord factor) and the mycolyl-arabinogalactan-peptidoglycan complex [2]. These components are essential for the structural integrity and virulence of the bacterium, providing a protective barrier against host immune responses and antibiotics [1]. Due to its high expression during early infection and its essential enzymatic role, Ag85B is a primary target for both novel antitubercular drugs and subunit vaccines [3]. Inhibiting this enzyme disrupts cell wall assembly, leading to bacterial death or increased susceptibility to other treatments [4]. Furthermore, Ag85B is highly immunogenic, making it a central component in several tuberculosis vaccine candidates currently in clinical trials, such as H56:IC31 and M72/AS01E [5]. The enzyme structure features an alpha/beta hydrolase fold with a catalytic triad (Ser124, Glu228, and His260) that is highly conserved across mycobacterial species [1]. Targeting Ag85B offers a strategy to bypass traditional antibiotic resistance mechanisms by focusing on extracellular cell wall assembly [3].

Other names

Antigen 85BAg85BFibronectin-binding protein BFbpB30 kDa extracellular proteinAlpha-antigen85B antigenRv1886c

Inhibition of mycolyltransferase activity to disrupt the synthesis of trehalose dimycolate and the mycolyl-arabinogalactan-peptidoglycan complex, essential components of the mycobacterial cell wall [1][2][3].