Abstract
Two different proteins having trypsin-inhibiting activity, referred to as inhibitors FI-a and FI-b, were purified from dried purple laver Porphyra yezoensis by haet treatment, ammonium sulfate fractionation, column chromatographies on a DEAF-cellulose and CM-cellulose and gel filtration on a Sephadex G-100. The inhibitory activities of both inhibitory against bovine trypsin increased about 4, 200-fold and 4, 500-fold, respectively. The molecular weights of both inhibitors were determined to be approximately 10, 000 by gel filtration on a Sephadex G-100. Both in-hibitors were stable over a range of pH 3.0-10.5 and at 60°C for 30 min. Trypsin was strongly inhibited by both inhibitors, α-chymotrypsin and pronase were weakly inhibited, but pepsin, papain and subtilisin BPN' were not inhibited. FI-a was completely inactivated by the modifica-tion of arginine residues with 1, 2-cyclohexanedione, but was not inactivated by the modification of lysine residues with O-methylisourea. Whereas, FI-b was inactivated by the modification with O-methylisourea, but was not inactivated by 1, 2-cyclohexanedione.
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