市販大豆トリプシンインヒビター (Kunitz) に含まれている高分子量インヒビターの分離と性質

概要

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Commercial Kunitz soybean trypsin inhibitor (STI) has been separated into two components, named STI-1 and STI-2, by gel filtration with Sephadex G-75. The molecular weights of STI-1 and STI-2 were estimated to be 41, 000_??_42, 000 and 20, 000_??_20, 500, respectively. The former was twice as large as the molecular weight of STI (20, 100) and the latter was identical with that of STI. The amino acid compositions of both STI-1 and STI-2 were in good agreement with that of STI. The trypsin and α-chymotrypsin inhibiting activities of STI-1 were low in comparison with those of STI-2. The trypsin inhibiting activity of STI-1 was 65% of STI-2. These results suggested that STI-1 was a dimer of STI-2.