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.