Abstract
The chemical reactivity of the disulfide bonds toward 0.1 M sodium borohydride and heat denaturation of the F4 inhibitor (Bowman-Birk inhibitor) were studied.
The disulfide bonds were completely reduced at 25°C for 1-2 hours, and the remaining inhibitory activities toward trypsin and α-chymotrypsin were 0-5% and 10-20%, respectively. At 0°C, most of the disulfide bonds were reduced for 5-7 hours, and the remaining inhibitory activities toward trypsin and α-chymotrypsin were 15% and 20%, respectively.
One disulfide bond could be reduced at 0°C for 75 minutes without loss of inhibitory activity toward both trypsin and α-chymotrypsin.
The solutions of the F4 inhibitor in 0.001 M HCl were heated at 100-200°C for 20 minutes. Depression of the inhibitory activity occurred at 135-140°C. At 200°C, the remaining inhibitory activity toward trypsin was 30-40%, whereas α-chymotrypsin inhibitory activity hardly remained.
The disulfide bonds were more or less affected by heat with the rise of temperature, and 1.3 M sulfhydryl groups were formed at 200°C for 20 minutes.
