Occurrence and Stabilities of Oat Trypsin and Chymotrypsin Inhibitors

Abstract

Nine chymotrypsin and four trypsin inhibitors have been extracted and separated from ungerminated oat grains. The inhibitors fell into two groups, based on their heat and pH stabilities. Members of the most abundant group are labile and are inactivated at 80 °C or at pHs of 3·3 or lower. Members of the second group are stable and are resistant to boiling for 30 min. On germination, the labile inhibitors are inactivated after 2 days and the stable chymotrypsin inhibitors after 3 days. Most of the labile inhibitors from ungerminated grain are destroyed when incubated at 20 °C for 20 h but addition of PMSF, a serine protease inhibitor, prevented their inactivation. Labile inhibitors in extracts of ungerminated oats are inactivated on incubation with an extract prepared from germinated oats, but not in the presence of PMSF. Most oat chymotrypsin and trypsin inhibitors are heat labile and pH sensitive. These inhibitors are apparently inactivated by serine proteinase(s) already present in ungerminated grain.