Bioactive function of alkaline protease inhibitor in soy bean miso.

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We tried to isolate alkaline protease inhibitor(API) and studied its physicochemical properties and bioactive function. The API activity was detected in two kinds of soy bean misos(Edo-miso and Saikyo-miso) and rice koji which is the raw material for processing soy bean miso. The inhibiting activity to AP was strong in the order of rice koji, Saikyo-miso and Edo-miso, when tested by using crude preparations of API. The API was further purified from rice koji by Sephadex G-50 gel filtration and DEAE-Toyopearl 650S ion exchenge column chromatography. The molecular weight of the purified API was about 20,000 and the pI was 5.6. The API activity was scarcely affected by heated at 70゜C for 30 min. Even heated at 100゜C for 20 min, 76% of the API activity was detected, so the API was high in heatstability. It showed the optimum pH at around 9 and was stable between pH9 and 11.Antimicrobial test was carried out by auto-biography using 8 species of microorganisms, but API did not suppress the growth of these species. But, API inhibits the cleavage of 32 to 64 stage fertilized egg of starfish(Asterina pectinifera) and the fact suggested the inhibitory function of API in DNA synthesis. From the result, API in miso may have some bioactive functions to human body such as suppressing the growth of eukaryotic organisms.