Purification and Chatacterization of Proteinase Inhibitors from Adzuki Beans (Phaseolus angularis)

抄録

Two proteinase inhibitors, designated as inhibitors I and II, were purified from adzuki beans (Phaseolus angularis) by chromatographies on DEAE- and CM-cellulose, and gel filtration on a Sephadex G-100 column. Each inhibitor shows unique inhibitory activities. Inhibitor I was a powerful inhibitor of trypsin [EC 3. 4. 21. 4], but essentially not of chyrnotrypsin [EC 3. 4. 21. 1]. On the other hand, inhibitor II inhibited chymotrypsin more strongly than trypsin. The molecular weights estimated from the enzyme inhibition were 3, 750 and 9, 700 for inhibitors I and II, respectively, assuming that the inhibitions were stoichiometric and in 1:1 molar ratio. The amino acid compositions of both inhibitors closely resemble those of low molecular weight inhibitors of other leguminous seeds: they contain large amounts of half-cystine, aspartic acid and serine, and little or no hydrophobic and aromatic amino acids. Inhibitor I lacks both tyrosine and tryptophan residues. The molecular weights were calculated to be 7, 894 and 8, 620 for inhibitors I and II, respectively. The reliability of these molecular weights was confirmed by the sedimentation equilibrium and 6_M guanidine gel filtration methods. On comparison with the values obtained from enzyme inhibition, it was concluded that inhibitor I had two trypsin inhibitory sites on the molecule, whereas inhibitor II had one chyrnotrypsin and one trypsin inhibitory sites on the molecule.