Characterising a new family of glycoside hydrolases that target mycobacterial cell wall glycans

The cell walls of pathogenic mycobacteria including the causative agent of Tuberculosis, M. tuberculosis, contribute to their pathogenicity and resistance to many common antibiotics.

We have discovered a novel family of enzymes expressed by glycan degrading bacteria from the human gut that are able to break down one of the most unusual components of the mycobacterial cell wall, 🇩-arabinan. 🇩-arabinan is a critical part of two different polymers of the mycobacteria cell wall, the structural glycan arabinogalactan, and the important immunomodulatory glycolipid lipoarabinomannan.

Excitingly, this new family of enzymes (AraH) has conserved homologues throughout mycobacteria, some of which have been previously identified in genetic screens to have a role in mycobacterial control of the phagosome. We hypothesise that mycobacteria use these enzymes to release the immunogenic lipoarabinomannan during infection.

This proposal aims to biochemically and structurally characterise members of the AraH family from pathogenic mycobacteria, including M. tuberculosis, M. abscessus, M. avium and M. leprae, with the ultimate aim of understanding their role in mycobacterial cell biology and infection.

We will express, purify and undertake detailed enzymatic analyses of these proteins, to characterise their activity towards arabinogalactan and lipoarabinomannan, and aim to obtain crystal structures to enable design of inhibitors.

These data will form the framework for future investigations into both the biological role of AraH in mycobacteria, and the potential of these enzymes as lytic tools for mycobacterial diagnostics.