Trypsinogen proenzyme forms

Trypsinogen, the inactive proenzyme form of trypsin has no water molecules in its unordered active site cf. Fehlhammer, H., Bode, W., Huber, R. ibid. Ill, 415 (1977)... 

Dietary proteins, with very few exceptions, are not absorbed rather they must be digested into amino acids, or di- and tripeptides. Protein digestion begins in the stomach, where proenzyme pepsinogen is autocatalytically converted to pepsin A. Most proteolysis takes place in the duodenum via enzymes secreted by the pancreas, including trypsinogen, chymotrypsinogen and pro-carboxypeptidase A. These serine and zinc proteases are produced in the form of their respective proenzymes they are both endopeptidase and exopeptidase, and their combined action leads to the production of amino acids, dipeptides and tripeptides. 

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