Inhibition of trypsin. The sequence of variant A is shown. Electrophoresis identifies three genetically distinct variants, A, B, and C, that are inherited as codominant alleles. Belongs to the protease inhibitor I3 (leguminous Kunitz-type inhibitor) family. PubMed:8318586 sequence was originally thought to be rat caltrin. A number of peptide fragments were derived from a trypsin digest of caltrin and soybean trypsin inhibitor was used to stop the digestion. It appears that some of the inhibitor was also digested and sequenced.