SOME PROPERTIES OF PROTEASE INHIBITORS IN WHEAT GRAIN

Abstract

General properties of the protease inhibitors in wheat and their distribution in germ, endosperm and bran were investigated. It was found that each part of wheat, germ, endosperm and bran, contains inhibitory activities against trypsin, α-chymotrypsin and pepsin. Gel electrophoresis of the germ extract revealed the presence of four trypsin inhibitors, three of which also had inhibitory activities against α-chymotrypsin. The endosperm portion was similarly shown to have three trypsin inhibitors, two of them having activities against α-chymotrypsin. One of the two trypsin inhibitors in bran also exhibited α-chymotrypsin-inhibitory activity. It was not, however, possible to identify pepsin inhibitors on the electrophotogram.
The trypsin inhibitors are moderately heat stable, retaining 90% of original activity after heating at 80°C for 2 hr. The α-chymotrypsin inhibitors, on the other hand, were found to be rather heat sensitive, losing 50% of its original activity upon heating at 80°C for 30min. This is contrasted by pepsin inhibitor which fully retains its original activity after heating in boiling water for 2 hr. Finally, molecular weights of the inhibitors were estimated by SDS-gel electrophoresis.