环乙烷中牛胰蛋白酶与正戊胺复合物的晶体结构

丝氨酸蛋白酶是有机溶媒中研究酶促反应的主要对象之一。其中的胰蛋白酶在 生物体内有重要的作用，对其抑制剂如苯甲脒衍生物的研究可应用于治疗很多疾病 。在水溶液中包括正太胺在内的开链脂肪胺类小分子对胰蛋白酶的抑制能力有限， 不能生成复合物。我们对浸泡在含有正戊胺的环已烷中的β-牛胰蛋白酶的晶体结 构进行了测定，分辨率为0.2 nm，并与水相中同样处理的晶体作了比较。结果表明 ，正戊胺于环已烷中和β-牛胰蛋白酶有强结合作用，一个戊胺分子结合到酶活性 中心；另一个结合在β-牛胰蛋白酶的表面，与也被结合的硫酸根形成氢键。此X射 线蛋白质晶体结构分析提供了一个例子，在有机溶剂中可用弱抑制剂的探针小分子 研究其和蛋白的结合情况，以及描绘蛋白质表面的结合位点。这些研究可以为搜索 弱抑制剂提供有用的结构信息。

Crystal Structure of β-Trypsin Complex with Amylamine in Cyclohexane

The X-ray structures of the crystals of bovine pancreatic β- trypsin soaked with amylamine as a probe were studied and compared in cydohexane and aqueous solution, respectively. It was shown that amylamine was occupied in the enzyme active site in cydohexane but not in aqueous solution. The crystal structure of the complex in cydohexane was determined at 0.2 nm resolution to a R-factor of 16.9% and a R_(free)-factor of 21.0% . The model includes one β-trypsin, two amylamine molecules, four sulfates, one calcium, and 135 water molecules. This X-ray structure analysis offers an approach to investigating an appropriate chemical compound to be an enzyme inhibitor or drug, and mapping the binding surface of crystalline protein with a probe which can bind to enzyme in organic medium but not in aqueous solution.