Summary for clan PC

Summary Alignment Structure Literature
Clan type peptidaseS51.001 - dipeptidase E (Salmonella enterica), MEROPS Accession MER0001336 (peptidase unit: 1-225); PDB accession 1FYE_A
HistoryMEROPS 6.1 (10 January 2003)
DescriptionSerine or cysteine nucleophile; catalytic residues in the order Cys (or Ser), His, Glu in sequence.
Contents of clanPeptidase clan PC contains cysteine and serine peptidases with varied types of activity.
EvidenceThe catalytic dyad occurs in the order Cys (or Ser), His in the sequence (see the Alignment and Protein fold).
Catalytic mechanism(See the family summaries: C26, C56 and S51).
Peptidase activityActivities are gamma-glutamyl hydrolase (C26.001), endopeptidase (C56.001) and dipeptidase (S51.001).
Protein foldStructures have been determined for gamma-glutamyl hydrolase (C26.001; Li et al., 2002), PfpI endopeptidase (C56.001; Du et al., 2000) and dipeptidase E (S51.001; Hakansson et al., 2000). Peptidases in clan PC have a fold containing a beta sheet (of five parallel strands, in the order 21345) sandwiched between two layers of alpha helices. The fold is similar to that of clan SC and other alpha/beta hydrolases, but is believed to be the result of convergent evolution (Hakansson et al., 2000). The nucleophile is conserved, but not the general base, which is always C-terminal to the nucleophile. In family C56 the active site Cys and His are adjacent residues and the only way to form an active site is by polymerization, with the active site formed between the interface of two monomers. Families C56 and S51 have active site triads, but the position of the third member, usually a Glu, is not conserved being N-terminal to the nucleophile in family C56 and C-terminal to the general base in S51.
Homologous non-peptidase familiesOther proteins with a similar fold include class I glutamine amidotransferase, the non-catalytic, middle domain of beta-galactosidase and the catalytic C-terminal domain of catalase (Li et al., 2002).
Other databases PFAMCL0014


Family Family Type Peptidase Structure
C26 gamma-glutamyl hydrolase (Rattus norvegicus) Yes
C56 PfpI peptidase (Pyrococcus furiosus) Yes
S51 dipeptidase E (Escherichia coli) Yes

Distribution of clan PC among Kingdoms of Organisms