【摘要】 研究了I型Kunitz大豆胰蛋白酶抑制剂(I-KSTI)和Bowman-Birk大豆胰蛋白酶抑制剂(BBTI)对胰蛋白酶的抑制活性及其二级结构的组成差异。发现I-KSTI及　BBTI对胰蛋白酶的抑制曲线分为两部分:活性急剧下降部分和缓慢下降部分。使胰蛋白酶的活性降为原来的一半时的I-KSTI和BBTI浓度为1.5μg/ml　和1.2μg/ml。使胰蛋白酶活性趋向于零(完全钝化)时的I-KSTI浓度为13.5μg/ml,而BBTI则为9μg/ml。两种抑制剂的存在不改变胰蛋白酶的Km值,但其Vmax随抑制剂浓度的增加而下降。表明其对胰蛋白酶的抑制作用是一种非竞争性抑制作用。远紫外圆二色谱的研究发现I-KSTI和BBTI的单一吸收负峰在200nm波长处,I-KSTI的克分子椭圆度[θ]200nm=-2545deg·cm2/d　mol,其二级结构由22.5%β折叠,16.25%β转角和61.4%无规卷曲组成;BBTI的[θ]200nm=-797deg·cm2/d　mol,由52.6%β折叠和47.4%无规卷曲组成。更多还原

【Abstract】 The inhibition curves of I-KSTI and BBTI against trypsin showed that the concentrations to attain 50% inhibitory ratio of trypsin activity were about 1.5μg/ml and 1.2μg/ml for I-KSTI and BBTI respectively. Complete inhibition concentrations against trypsin for BBTI and I-KSTI were 13.5μg/ml, 9μg/ml。In the presence of I-KSTI and BBTI, the Km value of trypsin was kept unchanged at 5.88×10-4 mol/L for benzoyl-DL Arginine-p-nitroanilide substrate while the Vmax was decreased. The far-UV CD (circular dichroism) spectra of both I-SKTI and BBTI showed a single negative peak at around 200nm and the negative minimum was measured as [θ]200nm=-2545deg.cm2/dmol for I-SKTI and [θ]200nm=-797deg.cm2/dmol for BBTI. The secondary structure of I-KSTI was composed of β-sheet (22.5%), β-turn (16.2%) and random (61.4%) whereas BBTI was composed only of β-sheet (52.6%) and random (47.4%).更多还原