Family M74


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family M74

Family type peptidaseM74.001 - murein endopeptidase (Escherichia coli), MEROPS Accession MER0001298 (peptidase unit: 20-274)
Content of familyPeptidase family M74 contains murein endopeptidase MepA.
History Identifier created: MEROPS 6.9 (16 December 2004)
Catalytic typeMetallo
Active site residuesH113 D120 H209 H211 
Active siteMepA (M74.001) is a metallopeptidase containing a single zinc ion bound by two histidines and an aspartate. The metal ligands occur in the motifs His-Xaa(6)-Asp and His-Xaa-His, which are characteristic of clan MD. His206 and His209 may be additional active site residues (Marcyjaniak et al., 2004).
Activities and specificitiesMepA hydrolyses the Ala-D-Glu-meso-diaminopimelateD-Ala bond in the crosslinking peptide and the Ala-D-Glu-meso-diaminopimelatemeso-diaminopimelate-D-Glu-Ala bond between crosslinking peptides. The pH optimum is 6.0 and divalent cations (Ca2+, Mg2+, Co2+) are required for activity (Templin & Holtje, 2004).
InhibitorsMepA is not inhibited by beta-lactam-derived antibiotics such as penicillin. DNA and polynucleotides are reported to be inhibitory (Templin & Holtje, 2004).
Molecular structureThe tertiary structure of MepA has been determined and is similar to that of D-Ala-D-Ala carboxypeptidases in family M15 (Marcyjaniak et al., 2004). Family M74 is therefore included in clan MD.
Distribution of family Bacteria details  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals details  
Viruses -  
Biological functionsThere are many peptidases involved in the synthesis and lysis of bacterial cell walls, and murein endopeptidase MepA hydrolyses the murein crosslinks. Unlike the peptidases in clan SE, MepA is insensitive to penicillin. No other peptidase activities are known from the family, and MepA has only been characterized from Escherichia coli. MepA is a periplasmic protein synthesized with a signal peptide. The enzyme is not essential because mepA- mutants are viable.
Statistics for family M74Sequences:377
Identifiers with PDB entries:1
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
murein endopeptidaseM74.001Yes
family M74 non-peptidase homologuesnon-peptidase homologue-
family M74 unassigned peptidasesunassigned-