Alagiri S, Singh T P
Department of Biophysics, All India Institute of Medical Sciences, New Delhi.
Biochim Biophys Acta. 1993 Nov 10;1203(1):77-84. doi: 10.1016/0167-4838(93)90038-s.
The stability of the bifunctional amylase/trypsin inhibitor from ragi (Indian finger millet, Eleusine coracana) has been studied by methods of circular dichroism, UV absorption and intrinsic fluorescence. The inhibitor is stable in 8 M urea and 6 M guanidine-HCl. In 150 mM NaCl, thermal denaturation does not occur up to 90 degrees C. However, it is irreversibly denatured in 5 mM NaCl if heated over 73 degrees C. The acidic denaturation is reversible in both high and low salt conditions, but it shows different behavior below pH 1.65 under similar salt conditions. The helical content is about 2-4% in the pH range of 7-9 at which the inhibitor is active maximally. The NaCl concentration does not have a significant effect on the secondary structure elements. The beta-strand form does not show much variation under various conditions. Arg34-Leu35 is the reactive peptide bond in the trypsin-binding site. Trp and Tyr are involved in the binding with amylase. The bifunctional inhibitor represents the sum of individual inhibitors of trypsin and amylase.
已通过圆二色性、紫外吸收和内源荧光等方法研究了龙爪稷（印度黍，龙爪稷）双功能淀粉酶/胰蛋白酶抑制剂的稳定性。该抑制剂在8 M尿素和6 M盐酸胍中稳定。在150 mM氯化钠中，高达90℃时不会发生热变性。然而，如果在5 mM氯化钠中加热超过73℃，它会发生不可逆变性。在高盐和低盐条件下，酸性变性都是可逆的，但在类似盐条件下，pH低于1.65时表现出不同行为。在抑制剂活性最大的pH范围7 - 9内，螺旋含量约为2 - 4%。氯化钠浓度对二级结构元件没有显著影响。β-链形式在各种条件下变化不大。Arg34 - Leu35是胰蛋白酶结合位点中的反应性肽键。色氨酸和酪氨酸参与与淀粉酶的结合。双功能抑制剂代表了胰蛋白酶和淀粉酶各自抑制剂的总和。
