Stomach

The stomach is the first point at which polypeptides are broken down. The low pH of the stomach causes enzymes to denature, opening them up to attack from proteases such as pepsin.

Pepsin

Pepsin is a powerful protease that cleaves at the N-terminus after aromatic amino acids such as phenylalanine, tryptophan, and tyrosine. The optimum pH of pepsin is from 1.5 to 2, at a pH of above 5 denaturation occurs. This means that pepsin is only functional in the acidic environment of the stomach.

One of the enzymes that we are showcasing is phenylalanine hydroxylase (PAH) (as a treatment for PKU). If this enzyme was simply swallowed in an unencapsulated form it would be rapidly broken down byb pepsin in the stomach.

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Duodenum

Endopeptidases (trypsin, chymotryopsin, elastase) Exopeptidases (carboxypeptidases A & B) Enteropeptidase

Trypsin

• Trypsin is found in the duodenum and serves to hydrolyse peptides into amino acids.
• Trypsin has an optimal operating pH of ~8 and an optimum temperature of 37°C.
• Trypsin breaks down the milk protein casein. For this reason, milk protein would be a good protein to use for secondary encapsulation.

Chymotryopsin

Elastase

Enterokinase

Carboxypeptidases A & B