Family S15


Summary Holotypes Alignment Tree Genomes Structure Literature H-seq M-seq

Summary for family S15

Family type peptidaseS15.001 - Xaa-Pro dipeptidyl-peptidase (Lactococcus lactis), MEROPS Accession MER0000443 (peptidase unit: 1-763)
Content of familyPeptidase family S15 contains Xaa-Pro dipeptidyl peptidase and its homologues.
History Identifier created: Biochem.J. 290:205-218 (1993)
Catalytic typeSerine
Active site residuesS348 D468 H498 
Active siteThe catalytic triad is in the order Ser348, His468, Asp498.
Activities and specificitiesXaa-Pro dipeptidyl-peptidase (S15.001) cleaves Xaa-Pro from the N-terminus of peptides provided that there is not a Pro in the P2 or P1" positions (Lloyd & Pritchard, 1991. It may also release Xaa-Ala and Xaa-Gly dipeptides, but more slowly than Xaa-Pro dipeptides (Khalid & Marth, 1990; Lloyd & Pritchard, 1991).
InhibitorsDFP and PMSF are both inhibitors of Xaa-Pro dipeptidyl-peptidase.
Molecular structureXaa-Pro dipeptidyl-peptidase is homodimeric with a 2-fold symmetry axis (Rigolet et al., 2002). There are four distinct domains. The largest is an alpha/beta hydrolase fold which contains the catalytic triad. The shortest domain is responsible for substrate binding specificity and is also involved in dimerisation. The N-terminus is mainly responsible for the dimerisation (Chich, 2004).
Basis of clan assignmentPredicted active site residues for members of this family and family S10 occur in the same order in the sequence: S, D, H.
Distribution of family Bacteria details  
Archaea details  
Protozoa details  
Fungi details  
Plants details  
Animals details  
Viruses -  
Biological functionsZevaco et al. (1990) and Lloyd & Pritchard (1991) have demonstrated that X-Pro dipeptidyl-peptidases are able to hydrolyze sequentially peptides derived from beta-casein. Therefore, it is believed that their role is in the degradation of caseins. It has been suggested that X-Pro dipeptidyl-peptidases have contrasting roles in the proteolytic systems of lactobacilli and lactococci (Chich, 2004). In lactobacilli X-Pro dipeptidyl-peptidase is involved in the casein-degradation pathway, providing essential amino acids to the lactobacilli (YŁksel & Steele, 1996). However, in lactococci X-Pro dipeptidyl-peptidase is not essential, but affects the peptide composition of fermented milk products (Mayo et al., 1993).
Statistics for family S15Sequences:6075
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
Xaa-Pro dipeptidyl-peptidaseS15.001Yes
family S15 non-peptidase homologuesnon-peptidase homologue-
family S15 unassigned peptidasesunassignedYes