Food Chemistry

1.4 Proteins 77

Table 1.33.

Classification of proteolytic enzymes (peptidases)

EC-No.

a

Enzyme group

Comments

Examples

Exopeptidases

Cleave proteins/peptidesstepwise from N- or C-terminals

3.4.11. Aminopeptidases

Cleave amino acids from N-terminal

Various aminopeptidases

3.4.13. Dipeptidases

Cleave dipeptides

Various dipeptidases (carnosinase, anserinase)

3.4.14. Dipeptidyl- and tripeptidylpeptidases Cleave di- and tripeptides from N-terminal

Cathepsin C

3.4.15. Peptidyl-dipeptidases

Cleave dipeptides from C-terminal

Carboxycathepsin,

3.4.16. Serine carboxypeptidases

Cleave amino acids from C-terminal, serine in the activesite

Carboxypeptidase C, cathepsin A

3.4.17. Metalocarboxypeptidases

Cleave amino acids from C-terminal, Zn

2 +

or Co

2 +

in

the active site

Carboxypeptidases A and B

3.4.18. Cysteine carboxypeptidases

Cleave amino acids from C-terminal, cysteine in the ac-tive site

Lysosomal carboxypeptidase B

Endopeptidases

Cleave protein/peptidebonds other than terminal ones

3.4.21. Serine endopeptidase

Serine in the active site

Chymotrypsins A, B and C, peptidase B alkaline pro-teinases

α

-and

β

-trypsin,

3.4.22. Cysteine endopeptidase

Cysteine in the active site

Papain, ficin, bromelain, cathepsin B

3.4.23. Aspartic endopeptidase

Aspartic acid (2 residues) in the active site

Pepsin, cathepsin D, rennin (chymosin)

3.4.24. Metaloendopeptidase

Metal ions in the active site

Collagenase, microbial neutral proteinases

a

cf. 2.2.7