Purification and Properties of a Trypsin Inhibitor from Barley

A trypsin inhibitor present in ungerminated barley in relatively high concentration (0.45 mg/g) has been obtained in apparently pure form. The inhibitor is a heat‐stable protein. Molecular weights of 14400 and 14055 were calculated from the sedimentation equilibrium and amino acid composition respectively. 1 μg of purified inhibitor inhibits 1.6–1.9 μg of pure trypsin in hydrolyses of casein, haemoglobin, and benzoyl‐dl‐arginine‐p‐nitroanilide. The inhibitor preparations are totally inactive against chymotrypsin and pepsin, proteolytic enzymes of germinating barley, and a number of microbial proteinases.