Table 1.
Classification and nomenclature of peptidases.
| Subclasses | EC code | Activity |
|---|---|---|
| Exopeptidases | 3.4.11–19 | Cleave near a terminus of peptides or proteins |
| Aminopeptidases | 3.4.11 | Remove a single amino acid from the free N-terminus |
| Dipeptidases | 3.4.13 | Exopeptidases specific for dipeptides |
| Dipeptidyl peptidases | 3.4.14 | Remove a dipeptide from the free N-terminus |
| Tripeptidyl peptidases | 3.4.14 | Remove a tripeptide from the free N-terminus |
| Peptidyldipeptidases | 3.4.15 | Release of free C-terminus liberates a dipeptide |
| Carboxypeptidases | 3.4.16–18 | Remove a single amino acid from the C-terminus |
| Serine proteases | 3.4.16 | Active sites contain serine |
| Metalloproteases | 3.4.17 | Active sites contain metal ions |
| Cysteine proteases | 3.4.18 | Active sites contain cysteine |
| Omega peptidases | 3.4.19 | Remove terminal residues that are substituted, cyclized or linked by isopeptide bonds |
| Endopeptidases | 3.4.21–24 | Cleave internally in peptides or proteins |
| Serine proteases | 3.4.21 | Active sites contain serine |
| Cysteine proteases | 3.4.22 | Active sites contain cysteine |
| Aspartic proteases | 3.4.23 | Active sites contain aspartate |
| Metalloproteases | 3.4.24 | Active sites contain metal ions |
| Threonine endopeptidases | 3.4.25 | Active sites contain threonine |
| Endopeptidases of unknown catalytic mechanism | 3.4.99 | Acting on peptide bonds |