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Updated: Aug 23, 2026
Semi-Quantitative Analysis of Peptidoglycan by Liquid Chromatography Mass Spectrometry and Bioinformatics
Published on: October 13, 2020
Peptidoglycan amidase MepA is a LAS metallopeptidase
Malgorzata Marcyjaniak1, Sergey G Odintsov, Izabela Sabala
1International Institute of Molecular and Cell Biology, ul. Trojdena 4, 02-109 Warsaw, Poland.
Abstract:
LAS enzymes are a group of metallopeptidases that share an active site architecture and a core folding motif and have been named according to the group members lysostaphin, D-Ala-D-Ala carboxypeptidase and sonic hedgehog. Escherichia coli MepA is a periplasmic, penicillin-insensitive murein endopeptidase that cleaves the D-alanyl-meso-2,6-diamino-pimelyl amide bond in E. coli peptidoglycan. The enzyme lacks sequence similarity with other peptidases, and is currently classified as a peptidase of unknown fold and catalytic class in all major data bases. Here, we build on our observation that two motifs, characteristic of the newly described LAS group of metallopeptidases, are conserved in MepA-type sequences. We demonstrate that recombinant E. coli MepA is sensitive to metal chelators and that mutations in the predicted Zn2+ ligands His-113, Asp-120, and His-211 inactivate the enzyme. Moreover, we present the crystal structure of MepA. The active site of the enzyme is most similar to the active sites of lysostaphin and D-Ala-D-Ala carboxypeptidase, and the fold is most closely related to the N-domain of sonic hedgehog. We conclude that MepA-type peptidases are LAS enzymes.
Insights
Escherichia coli MepA, a murein endopeptidase, is identified as a LAS enzyme. This study reveals its metallopeptidase activity and structural similarity to known LAS enzymes.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- LAS enzymes are metallopeptidases with conserved active site and folding motifs.
- Escherichia coli MepA is a periplasmic, penicillin-insensitive murein endopeptidase.
- MepA lacks sequence similarity to other peptidases and is unclassified.
Purpose of the Study:
- To investigate the classification of E. coli MepA within the LAS enzyme group.
- To characterize the enzymatic activity and structural features of MepA.
- To determine if MepA shares conserved motifs with LAS enzymes.
Main Methods:
- Sequence analysis to identify conserved motifs.
- Enzymatic assays using metal chelators.
- Site-directed mutagenesis of predicted metal ligands (His-113, Asp-120, His-211).
- X-ray crystallography to determine MepA's structure.
Main Results:
- MepA exhibits conserved motifs characteristic of LAS enzymes.
- Recombinant MepA is sensitive to metal chelators.
- Mutations in predicted Zn2+ ligands inactivate MepA.
- Crystal structure reveals active site similarity to lysostaphin and D-Ala-D-Ala carboxypeptidase.
- MepA's fold is related to the N-domain of sonic hedgehog.
Conclusions:
- E. coli MepA is classified as a LAS enzyme.
- MepA functions as a zinc metallopeptidase.
- Structural and sequence similarities confirm MepA's place within the LAS family.
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