Trypsin-1 is  a trypsinogen, which is a member of the trypsin family of serine proteases. This enzyme is secreted by the pancreas and cleaved to its active form in the small intestine. It is active on peptide linkages involving the carboxyl group of lysine or arginine. Mutations in this gene are associated with hereditary pancreatitis. This gene and several other trypsinogen genes are localized to the T cell receptor beta locus on chromosome 7.

Normally, cationic trypsinogen represents approximately two-thirds of total trypsinogen, while anionic trypsinogen makes up approximately one-third. Mesotrypsinogen is a minor species, accounting for less than 5% of trypsinogens or 0.5% of pancreatic juice proteins.