Family C66


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C66

Family type peptidaseC66.001 - IdeS peptidase (Streptococcus pyogenes), MEROPS Accession MER0030090 (peptidase unit: 1-339)
Content of familyPeptidase family C66 contains a bacterial endopeptidase.
History Identifier created: MEROPS 6.4 (24 September 2003)
The IdeS peptidase (also termed Mac protein) of Streptococcus pyogenes was discovered in 2001 as a factor contributing to evasion of immunity in the human host by this pathogenic organism (Lei et al., 2001). It was found that the protein has homology to human CD11b (in residues 139-322 of Mac). The endopeptidase activity of the protein against immunoglobulin G (IgG) was recognised by Pawel-Rammingen et al., 2002.
Catalytic typeCysteine
Active site residuesC94 H262 D,E284 D,N286 
Active siteThe catalytic residues of IdeS peptidase are apparent from the structure (Wenig et al., 2004), and are Cys94, His262 and Asp284 (see the Alignment).
Activities and specificitiesThe IdeS peptidase cleaves both gamma chains of human IgG or its Fc fragment in the hinge region after Gly236 (Vincents et al., 2004). No other natural or artificial substrate could be identified. The Gly236 bond is also cleaved by streptopain (C10.001).
InhibitorsIodoacetate and iodoacetamide inhibited IdeS, but there was no inhibiton by compound E-64 or chicken cystatin (I25.011) (Vincents et al., 2004).
Molecular structureThe crystal structure of a catalytically inactive form of C66.001, IdeS-C94S, shows a divergent, papain-like fold, and justifies inclusion of family C66 in clan CA, consistent with the Cys/His/Asp arrangement of catalytic residues (Wenig et al., 2004).
Distribution of family Bacteria details  
Archaea -  
Protozoa details  
Fungi -  
Plants -  
Animals -  
Viruses -  
Biological functionsThe IdeS peptidase is secreted in a form that does not require processing to exert its peptidase activity (thus differing from streptopain and many other peptidases of clan CA). It has the ability to inhibit IgG-mediated phagocytosis by human polymorphonuclear leucocytes, but the inhibition of phagocytosis is not dependent upon the peptidase activity (Lei et al., 2002).
Statistics for family C66Sequences:60
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
IdeS peptidaseC66.001Yes
IdeSsuis peptidase (Streptococcus suis)C66.003-
family C66 non-peptidase homologuesnon-peptidase homologue-
family C66 unassigned peptidasesunassigned-