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Updated: Jul 11, 2025
Analysis of the Lipid Composition of Mycobacteria by Thin Layer Chromatography
Published on: April 16, 2021
The mycobacterial glycoside hydrolase LamH enables capsular arabinomannan release and stimulates growth
Aaron Franklin1, Abigail J Layton1, Todd Mize1
1School of Biosciences, University of Birmingham, Birmingham, U.K., B15 2TT.
Abstract:
Mycobacterial glycolipids are important cell envelope structures that drive host-pathogen interactions. Arguably, the most important amongst these are lipoarabinomannan (LAM) and its precursor, lipomannan (LM), which are both trafficked out of the bacterium to the host via unknown mechanisms. An important class of exported LM/LAM is the capsular derivative of these molecules which is devoid of its lipid anchor. Here, we describe the identification of a glycoside hydrolase family 76 enzyme that we term LamH which specifically cleaves α-1,6-mannoside linkages within LM and LAM, driving its export to the capsule releasing its phosphatidyl-myo-inositol mannoside lipid anchor. Unexpectedly, we found that the catalytic activity of this enzyme is important for efficient exit from stationary phase cultures where arabinomannan acts as a signal for growth phase transition. Finally, we demonstrate that LamH is important for Mycobacterium tuberculosis survival in macrophages. These data provide a new framework for understanding the biological role of LAM in mycobacteria.
Insights
Researchers discovered LamH, an enzyme crucial for exporting mycobacterial lipoarabinomannan (LAM) and lipomannan (LM) from the cell. This enzyme is vital for Mycobacterium tuberculosis survival in macrophages and bacterial growth phase transitions.
Area of Science:
- Microbiology
- Glycobiology
- Host-Pathogen Interactions
Background:
- Mycobacterial cell envelopes contain essential glycolipids like lipoarabinomannan (LAM) and lipomannan (LM) that mediate host-pathogen interactions.
- The export mechanisms for these critical molecules remain largely unknown.
- A capsular derivative of LM/LAM, lacking its lipid anchor, is a significant exported form.
Approach:
- Identification of a novel glycoside hydrolase family 76 enzyme, designated LamH.
- Demonstration of LamH's specific cleavage of α-1,6-mannoside linkages in LM and LAM.
- Investigation of LamH's role in LM/LAM export, lipid anchor release, and bacterial survival.
Key Points:
- LamH specifically cleaves α-1,6-mannoside linkages in lipomannan (LM) and lipoarabinomannan (LAM), facilitating their export and releasing the lipid anchor.
- The enzyme's activity is unexpectedly critical for exiting stationary phase cultures, with arabinomannan signaling growth phase transition.
- LamH plays a significant role in the survival of Mycobacterium tuberculosis within macrophages.
Conclusions:
- LamH provides a novel mechanism for the export of mycobacterial glycolipids.
- This enzyme is essential for Mycobacterium tuberculosis pathogenesis and survival.
- The findings offer a new perspective on the biological functions of LAM in mycobacteria.
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