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Updated: May 16, 2026
11:27
X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
Functional characterization of two M42 aminopeptidases erroneously annotated as cellulases
Raphaël Dutoit1, Nathalie Brandt, Christianne Legrain
1Institut de Recherches Microbiologiques JM Wiame, Brussels, Belgium. rdutoit@ulb.ac.be
Plos One
|December 11, 2012
Summary
Members of the M42 aminopeptidase family, including CelM and TmPep1050, function as aminopeptidases, not cellulases. This finding clarifies their role in peptide degradation and impacts enzyme annotation across archaea and bacteria.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- The M42 family of aminopeptidases, often tetrahedral-shaped dodecameric (TET) enzymes, are hypothesized to degrade proteasome-generated peptides.
- Some M42 members are misannotated as cellulases due to homology with CelM, previously identified as an endoglucanase.
Purpose of the Study:
- To investigate the catalytic functions and substrate specificities of CelM and TmPep1050.
- To clarify the enzymatic roles within the M42 aminopeptidase family and correct potential misannotations.
Main Methods:
- Enzyme activity assays using nonpolar aliphatic L-amino acid-pNA substrates.
- Testing the effects of cobalt ions, EDTA, and bestatin on enzyme activity.
- Bioinformatic analysis of M42 aminopeptidase distribution across microbial phyla.
Main Results:
- CelM and TmPep1050 exhibited significant aminopeptidase activity, with a preference for L-leucine derivatives.
- No significant endoglucanase activity was detected for either enzyme.
- Enzyme activity was enhanced by cobalt ions and inhibited by EDTA and bestatin, confirming metalloaminopeptidase function.
- TET aminopeptidases are widespread in archaea and bacteria, but some phyla lack both TET and tricorn peptidases.
Conclusions:
- Members of the M42 aminopeptidase family should not be annotated as cellulases.
- The distribution patterns suggest alternative proteasome-downstream peptide degradation pathways in certain microbial lineages.
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