Trypsin
Trypsin is an
enzyme that cleaves
proteins at specific positions. It cuts at R-X and K-X bonds, unless X is P (see
amino acids for the codes). Many trypsin preparations contain some
chymotrypsin activity. The
pH optimum for trypsin activity is pH 7-9, and it is permanently inactivated at pH > 11. Trypsin retains activity in 0.1%
SDS, 1 M guanidine
HCl, and 30%
ethanol. The autocatalytic activity of trypsin can be slowed down with 20 mM calcium.
Together with pepsin and chymotrypsin, trypsin is one of the three principal digestive proteinases. It is produced by the pancreas, and works in the small intestine, where it degrades proteins to polypeptides and amino acids.