Some Properties of Proteinase Inhibitors from Adzuki Beans (Phaseolus angularis)

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Abstract
Proteinase inhibitors I and II from adzuki beans were very stable even at 100°C in acidic pH range. Inhibitor I was a polypeptide chain having aspartic acid as a carboxyterminal residue and inhibitor II was that having asparagine. Inhibitor I may have two different reactive sites against trypsin and one of them will be a particular Lys-X peptide bond, judging from the fact that about 50% of the inhibitory activity against trypsin remained, even if 80% of the amino-groups were modified by trinitrobenzenesulfonic acid. Inhibitor II inhibited trypsin and chymotrypsin separately, but not simultaneously. The inhibitor, however, could be said to have separate and independent reactive sites against the enzymes, because the reaction of inhibitor II with trinitrobenzenesulfonic acid abolished the tryptic inhibitory activity of the inhibitor, but left the chymotryptic inhibitory activity intact.