Main proteases with their cleavage site and proteolytic mechanism
| Proteases | EC | Proteolytic mechanism | Cleavage site |
|---|---|---|---|
| Asn lyases* | 4.3.2 | Elimination reaction | Asn-Ala bond |
| Aspartic peptidases | 3.4.23 | Acid-base | Cys |
| Cys peptidases | 3.4.22 | Catalytic | C-terminal Asn |
| Glutamate peptidases* | 3.4.23 | Hydrolysis | NAA-Glu |
| Metallopeptidades | 3.4.24 | Catalytic | Metal-binding residues (i.e. His, Glu, Asp) |
| Serine peptidases | 3.4.21 | Acyl-enzyme intermediate | Aromatic amino acids (i.e. Phe-Thr, Tyr-Ser) |
| Threonine peptidases | 3.4.25 | N-terminus hydrolysis | N-terminal Met |
* At present not found in mammals (isolated from fungal and bacterial sources). EC: enzymatic class; NAA: N-acetyl aspartate; Asn: asparagine; Ala: alanine; Cys: cysteine; Glu: glutamic acid; His: histidine; Asp: aspartic acid; Phe: phenylalanine; Thr: threonine; Tyr: tyrosine