Occurrence and stabilities of oat trypsin and chymotrypsin inhibitors

Nine chymotrypsin and four trypsin inhibitors have been extracted and separ ated from ungerminated oat grains. The inhibitors fell into two groups, bas ed on their heat and pH stabilities. Members of the most abundant group are labile and are inactivated at 80 degrees C or at pHs of 3.3 or lower. Memb ers 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 degrees C for 2 0 h but addition of PMSF, a serine protease inhibitor, prevented their inac tivation. Labile inhibitors in extracts of ungerminated oats are inactivate d on incubation with an extract prepared from germinated oats, but not in t he presence of PMSF. Most oat chymotrypsin and trypsin inhibitors are heal labile and pH sensitive. These inhibitors are apparently inactivated by ser ine proteinase(s) already present in ungerminated grain. (C) 1999 Academic Press.