Eder J, Rheinnecker M, Fersht A R
MRC Unit for Protein Function and Design, University Chemical Laboratory, Cambridge, UK.
FEBS Lett. 1993 Dec 13;335(3):349-52. doi: 10.1016/0014-5793(93)80417-s.
Variants of subtilisin BPN' that possess improved specificity towards isoleucine compared with alanine at the P4 position of small peptide substrates, were analysed for their ability to bind chymotrypsin inhibitor 2. The binding of the inhibitor with isoleucine (wild-type) and with alanine as the P4 residue parallels the hydrolysis of tetrapeptide substrates. There is a linear relationship between the free energy of binding of the transition state of the substrate and the free energy of binding of the inhibitor with a slope of 2.0. The data suggest that the inhibitor uses predominantly ground state rather than transition state binding energy.
与小肽底物P4位置上的丙氨酸相比，对异亮氨酸具有更高特异性的枯草杆菌蛋白酶BPN'变体，被分析了它们结合胰凝乳蛋白酶抑制剂2的能力。抑制剂与异亮氨酸（野生型）以及与作为P4残基的丙氨酸的结合，与四肽底物的水解情况相似。底物过渡态结合的自由能与抑制剂结合的自由能之间存在线性关系，斜率为2.0。数据表明，该抑制剂主要利用基态而非过渡态结合能。
