Table 1.
Enzymes involved in protein digestion, their products and detection methods.
| Enzyme (Source) | Function | Product | Detection | Substrate | Wave Length |
|---|---|---|---|---|---|
| Endopeptidase | |||||
| Pepsin (stomach) | Cleavage peptides with aromatic AA | Peptide (AA) | F | Synthetic peptide substrate | Ex: 328 nm Em: 418 nm |
| Trypsin (pancreas) | Cleavage peptides with basic AA | Peptide (AA) | A | Synthetic substrate | 405 nm |
| Chymotrypsin (pancreas) |
Cleavage peptides with aromatic AA and tryptophan | Peptide (AA) | F | Synthetic fluorogenic substrate | Ex: 380 nm Em: 460 nm |
| Elastase (pancreas) | Cleavage peptides with neutral AA without ring system | Peptide (AA) | F | Synthetic substrate | Ex: 380 nm Em: 500 nm |
| Exopeptidase | |||||
| Carboxypeptidase A (pancreas) |
Cleavage peptides with C-terminal AA | AA, Peptide | A | N-(4-methoxyphenylazoformyl)-Phe-OH potassium salt | 350 nm |
| Carboxypeptidase B (pancreas) |
Cleavage peptides with C-terminal basic AA | AA, Peptide | A | N-(4-methoxyphenylazoformyl)-Arg-OH HCl | 350 nm |
| Aminopeptidase (BBM) | Cleavage peptides with C-terminal AA | AA, Peptide | F | Fluorogenic substrate | Ex: 384 nm Em: 502 nm |
| Other Peptidase | |||||
| y-Glutamyl-transpeptidase (BBM) | Cleavage the AA glutamic acid from the tripeptide glutathione | AA, Dipeptide | A | L γ Glutamyl pNA | 418 nm |
| Dipeptidyl-peptidase (BBM) | Cleavage the AA glutamic acid from the tripeptide glutathione | Dipeptide, Peptide | F | Synthetic substrate | Ex: 360 nm Em: 460 nm |
Modified from [17]; BBM, brush border membrane; F, fluorescence; A, absorbance; EX, excitation; EM, emission.