1 Food Biochemistry—An Introduction 11Table 1.5.Proteases in Animal Tissues and Their Degradation
Enzyme Reaction
Acid/aspartyl proteases
Pepsin A (Pepsin, EC 3.4.23.1) Preferential cleavage, hydrophobic, preferably aromatic,
residues in P1 and P1 positions
Gastricsin (pepsin C, EC 3.4.23.3) More restricted specificity than pepsin A; high preferential
cleavage at Tyr bond
Cathepsin D (EC 3.4.23.5) Specificity similar to, but narrower than that of pepsin A
Serine proteases
Trypsin (- and -trypsin, EC 3.4.21.4) Preferential cleavage: Arg-, Lys-
Chymotrypsin (Chymotrypsin A and B, Preferential cleavage: Tyr-, Trp-, Phe-, Leu-
EC 3.4.21.1)
Chymotrysin C (EC 3.4.21.2) Preferential cleavage: Leu-, Tyr-, Phe-, Met-, Trp-, Gln-, Asn-
Pancreatic elastase (pancreato- Hydrolysis of proteins, including elastin. Preferential
peptidase E, pancreatic elastase I, cleavage: Ala
EC 3.4.21.36)
Plasmin (fibrinase, fibrinolysin, Preferential cleavage: Lys- Arg-; higher selectivity
EC 3.4.21.7) than trypsin
Enteropeptidase (enterokinase, Activation of trypsinogen be selective cleavage of Lys^6 -Ile^7
EC 3.4.21.9) bond
Collagenase General term for hydrolysis of collagen into smaller
molecules
Thio/cysteine proteases
Cathepsin B (cathepsin B1, EC 3.4.22.1) Hydrolysis of proteins, with broad specificity for peptide
bonds, preferentially cleaves -Arg-Arg- bonds in small
molecule substrates
Papain (EC 3.4.22.2) Hydrolysis of proteins, with broad specificity for peptide
bonds, but preference for an amino acid bearing a large
hydrophobic side chain at the P2 position. Does not accept
Val in P1
Fiacin (ficin, EC 3.4.23.3) Similar to that of papain
Bromelain (3.4.22.4) Broad specificity similar to that of pepsin A
-glutamyl hydrolase (EC 3.4.22.12 Hydrolyzes -glutamyl bonds
changed to 3.4.1.99)
Cathepsin H (EC 3.4.22.16) Hydrolysis of proteins; acts also as an aminopeptidase
(notably, cleaving Arg bond) as well as an endopeptidase
Calpain-1 (EC 3.4.22.17 changed to Limited cleavage of tropinin I, tropomyosin, and C-protein
3.4.22.50) from myofibrils and various cytoskeletal proteins from
other tissues. Activates phosphorylase, kinase, and cyclic-
nucleotide-dependent protein kinase
Metalloproteases
Procollagen N-proteinase (EC 3.4.24.14) Cleaves N-propeptide of procollagen chain 1(I) at Pro
Gln and 1(II) and 2(I) at AlaGln
Sources:Eskin 1990, Haard 1990, Lowrie 1992, Huff-Lonergan and Lonergan 1999, Gopakumar 2000, Jiang 2000,
Simpson 2000, Greaser 2001, IUBMB-NC website (www.iubmb.org).