A trypsin inhibitor (TI) is a protein and a type of serine protease inhibitor (serpin) that reduces the biological activity of trypsin by controlling the activation and catalytic reactions of proteins. Trypsin is an enzyme involved in the breakdown of many different proteins, primarily as part of digestion in humans and other animals such as monogastrics and young ruminants. Serpins – including trypsin inhibitors – are irreversible and suicide substrate-like inhibitors.

It destructively alters trypsin thereby rendering it unavailable to bind with proteins for the digestion process. As a result, protease inhibitors that interfere with digestion activity have an antinutritional effect. Therefore, trypsin inhibitors are considered an anti-nutritional factor or ANF. Additionally, trypsin inhibitor partially interferes with chymotrypsin function.

Trypsinogen is an inactive form of trypsin, its inactive form ensures protein aspects of the body, such as the pancreas and muscles, are not broken down. It is formed in the pancreas and activated to trypsin with enteropeptidase Chymotrypsinogen is the inactive form of chymotrypsin and has similar functions as trypsin.

The presence of trypsin inhibitor has been found to result in delayed growth as well as metabolic and digestive diseases. Additionally, pancreatic hypertrophy is a common occurrence with trypsin inhibitor consumption The presence of trypsin inhibitor in a product reduces the protein efficiency and therefore results in the consumers body not being able to efficiently and fully utilize the protein.