(Peptidyl peptide hydrolase; EC 18.104.22.168)
Trypsin is an important proteolytic enzyme which is widely distributed in
animals and in some bacteria. Trypsinogen is the inactive precursor of trypsin,
which is secreted by the exocrine cells of the pancreas and then released into
the lumen of the small intestine. Trypsinogen is converted to the active trypsin
by enterokinase from the intestinal mucosa and by trypsin itself.
Trypsin is an endopeptidase and it hydrolyzes peptide bonds in which the carbonyl
group is contributed by the basic amino acids lysine or arginine. The optimum
pH for trypsin is in the range of 7-9. Calcium ions contribute to increasing
the stability of trypsin, while several proteinlike substances inhibit the activity
of trypsin. These trypsin inhibitors have been isolated from soybean, barley,
mung bean and pancreas.