Table 1.

A list of characterized M23 peptidases, their sources, specificities, and biological roles.

Protein	Original organism	M23 catalytic domain activity	Specificity	Role	PDB ID	References
Lysostaphin (Lss)	Staphylococcus simulans biovar staphylolyticus	Glycyl-glycine endopeptidase	Gly-Gly	Bacteriocin	4QPB 4LXC	Schindler and Schuhardt, 1964; Simmonds et al., 1996; Bastos et al., 2010; Sabala et al., 2014; Tossavainen et al., 2018
LytM	Staphylococcus aureus	Glycyl-glycine endopeptidase	Gly-Gly	Autolysin	1QWY 2B44 2B13 2B0P 4ZYB	Odintsov et al., 2004; Firczuk et al., 2005; Grabowska et al., 2015
LytU	Staphylococcus aureus	Glycyl-glycine endopeptidase	Gly-Gly	Bacteriocin/Peptidoglycan remodeling	5KQB 5KQC	Raulinaitis et al., 2017
ALE-1	Staphylococcus capitis EPK1	Glycyl-glycine endopeptidase	Gly-Gly	Bacteriocin	-	Fujiwara et al., 2005
SpM23_A	Staphylococcus pettenkoferi	Glycyl-glycine endopeptidase	Gly-Gly	Autolysin	-	Wysocka et al., 2021
SpM23_B	Staphylococcus pettenkoferi	Glycyl-glycine endopeptidase	Gly-Gly	Bacteriocin	-	Wysocka et al., 2021
gp13	Bacillus subtilis phage ф29	D,D-endopeptidase	D-Ala-Dpm	Phage tail-associated peptidoglycan hydrolase	3CSQ	Xiang et al., 2008
Csd2	Helicobacter pylori	D,D-endopeptidase	D-Ala-Dpm	Cell shape determinant	5J1K 5J1M	An et al., 2016
ShyA	Vibrio cholerae	D,D-endopeptidase	D-Ala-Dpm	Growth promoting endopeptidase	2GU1 6U2A 6UE4	Shin et al., 2020
YebA	Escherichia coli	D,D-endopeptidase	D-Ala-Dpm	Peptidoglycan turnover	-	Singh et al., 2012
NMB0315	Neisseria meniningitids	D,D-endopeptidase	D-Ala-Dpm	Bacterial virulence	3SLU	Wang et al., 2011
CwlP	Bacillus subtills SP-β-prophage	D,D-endopeptidase	D-Ala-Dpm	Phage encoded endolysin		Sudiarta et al., 2010
Csd3 (HdpA)	Helicobacter pylori	D,D-endopeptidase D,D-carboxypeptidase	D-Ala-Dpm D-Ala- D-Ala	Cell shape determinant	4RNY 4RNZ	An et al., 2015
Pgp3	Campylobacter jejuni	D,D-endopeptidase D,D-carboxypeptidase	D-Ala- Dpm D-Ala- D-Ala	Peptidoglycan reshaping	6JMX 6JM 6KV1 6JN0 6JN1 6JMZ 6JN7 6JN8	Min et al., 2020
LytH (YunA)	Bacillus subtilis	L,D-endopeptidase	L-Ala-D-Glu	Spore cortex formation		Horsburgh et al., 2003
Enterolysin A	Enterococcus faecalis B9510	L,D-endopeptidase	L-Ala-D-Glu; L-Lys-D-Asp	Bacteriocin	-	Nilsen et al., 2003; Khan et al., 2013
2638A endolysin	Staphylococcus aureus phage 2638A	D,L- endopeptidase	D-Ala-Gly	Phage encoded endolysin	6YJ1	Abaev et al., 2013; Eichenseher et al., 2022
EnpA	Enterococcus faecalis phage 03	D,L-endopeptidase	D-Ala- Gly/Ala/Ser	Phage encoded endolysin	6SMK	Reste de Roca et al., 2010; Małecki et al., 2021
Zoocin A	Streptococcus equi subsp. zooepidemicus 4,881	D,L-endopeptidase	D-Ala-L-Ala	Bacteriocin	5KVP	Simmonds et al., 1996; Akesson et al., 2007; Xing et al., 2017
LasA	Pseudomonas aeruginosa	Endopeptidase	Gly -Gly/Tyr/Leu/Phe	Bacterial virulence	3IT5 3IT7	Grande et al., 2007; Spencer et al., 2010
Pseudoalterin	Pseudoalteromonas sp. strain CF6-2	Endopeptidase	Gly-Gly/Ala D-Ala-D-Ala D-Ala-L-Lys L-Lys-D-Ala Desmosine-Ala-Ala Desmosine-Ala-Ala-Ala	Elastin degradation in marine vertebrates	6IK4	Zhao et al., 2012; Tang et al., 2020
Fibronectin binding proteins (e.g., TDE1738)	Trepanoma denticola	Endopeptidase	Unknown	Fibronectin-binding protein	-	Bamford et al., 2010
Tal2009	Lactococcus lactis subsp. cremoris UC509 phage Tuc2009	Endopeptidase	Unknown	Phage tail-associated lysin		Kenny et al., 2004
Atu4178	Agrobacterium tumefaciens	Endopeptidase	Unknown	Polar growth		Figueroa-Cuilan et al., 2021
EnvC	Escherichia coli	LytM factor	-	Septum-specific activation of amidase AmiA/B	-	Uehara et al., 2009; Peters et al., 2013
NlpD	Escherichia coli	LytM factor	-	Septum-specific activation of amidase AmiC	-	Uehara et al., 2009; Peters et al., 2013
DipM	Caulobacter crescentus	LytM factor	-	Peptidoglycan remodeling	-	Goley et al., 2010; Möll et al., 2010