Family C10


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C10

NamePeptidase family C10 (streptopain family)
Family type peptidaseC10.001 - streptopain (Streptococcus pyogenes), MEROPS Accession MER0001346 (peptidase unit: 146-398)
Content of familyPeptidase family C10 contains bacterial cysteine endopeptidases.
History Identifier created: Biochem.J. 290:205-218 (1993)
Family C10 contains streptopain (C10.001) (Watts & Brocklehurst, 2004) and a few homologues that have not been characterised in detail.
Catalytic typeCysteine
Active site residuesC192 H340 
Active siteStreptopain contains only a single Cys residue. The catalytic His residue C-terminal to this was identified by mutagenesis (Gubba et al., 2000). The crystal structure (Kagawa et al., 2000) confirms the catalytic His, and a Gln shortly preceding the Cys. However, there is no Asn or Asp residue equivalent to the Asn that completes the catalytic triad in most peptidases in clan CA; Kagawa et al. (2000) suggest that the carbonyl group of a Trp residue may serve a similar function.
Activities and specificitiesStreptopain has broad, generally papain-like specificity, the major specificity determinant being a hydrophobic residue in the P2 position.
InhibitorsStreptopain is inhibited by common cysteine peptidase inhibitors such as iodoacetate, iodoacetamide, N-ethylmaleimide, p-chloromercuribenzoate, metallic ions (Cu2+, Hg2+ and Ag+) and atmospheric oxygen (Liu & Elliott, 1965). 2,2"-Dipyridyl disulfide serves as an active center titrant (French et al., 1990). Other peptidases in the family can be expected to behave similarly.
Molecular structureThe proenzyme and the active peptidase each contain only a single cysteine residue (Cys131, proenzyme numbering), so both proteins lack disulfide bonds. The crystal structure of the proenzyme of a recombinant Cys47Ser mutant of streptopain (as SpeB) at 1.6 Å was described by Kagawa et al. (2000), and shows a protein fold that is closely similar to those of peptidases in family C1, supporting the assignment of family C10 to clan CA.
Basis of clan assignmentProtein fold of the peptidase unit for members of this family and resembles that of papain, the type example for clan CA.
Distribution of family Bacteria details  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses -  
Biological functionsIt seems likely that streptopain contributes to the virulence of Streptococcus pyogenes as a pathogen at least under some circumstances, although there is controversy about this (Ashbaugh et al., 2001; Hytönen et al., 2001). Detection of streptopain is reported to be of diagnostic value for Streptococcus pyogenes infections (Batsford et al., 2002). Streptopain is pyrogenic exotoxin B.
Statistics for family C10Sequences:230
Identifiers with PDB entries:2
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
PrtT peptidaseC10.002-
interpain AC10.004Yes
family C10 unassigned peptidasesunassigned-