Takahashi K, Sturtevant J M
Biochemistry. 1981 Oct 13;20(21):6185-90. doi: 10.1021/bi00524a042.
The thermal unfolding of the microbial proteinase inhibitor Streptomyces subtilisin inhibitor (SSI) [Sato, S., & Murao, S. (1973) Agric, Biol. Chem. 37, 1067-1074), the bacterial proteinase subtilisin BPN' (EC 3.4.21.14), and the complex formed by these two proteins has been studied by differential scanning calorimetry (DSC). The thermal denaturation of SSI at pH 7.00 is fully reversible while those of subtilisin BPN' and its complex with SSI are not. The DSC data show that dimeric SSI remains dimeric as the temperature is raised until it unfolds and that it then dissociates during the unfolding process. The apparent specific heat of denatured SSI decreases rapidly with increasing temperature, a behavior not previously observed for proteins. The shape of the DSC curves observed with the enzyme-inhibitor complex suggests that the two components of the complex undergo their unfolding transitions more or less independently. The enthalpies of unfolding of mixtures of enzyme and inhibitor in various molar ratios indicate a substantially large enthalph of interaction than that deduced from fluorescence titrations (Uehara, Y., Tonomura, B., & Hiromi, K. (1978) J. Biochem. (Tokyo) 84, 1195-1202).
利用差示扫描量热法（DSC）研究了微生物蛋白酶抑制剂枯草芽孢杆菌蛋白酶抑制剂（SSI）[佐藤，S.，& 村尾，S.（1973年）《农业与生物化学》37卷，第1067 - 1074页]、细菌蛋白酶枯草杆菌蛋白酶BPN'（EC 3.4.21.14）以及由这两种蛋白质形成的复合物的热解折叠过程。在pH 7.00条件下，SSI的热变性是完全可逆的，而枯草杆菌蛋白酶BPN'及其与SSI形成的复合物的热变性则不可逆。DSC数据表明，二聚体SSI在温度升高直至解折叠之前一直保持二聚体状态，然后在解折叠过程中发生解离。变性SSI的表观比热随温度升高而迅速降低，这种行为在蛋白质中此前未曾观察到。酶 - 抑制剂复合物的DSC曲线形状表明，复合物的两个组分或多或少独立地经历其解折叠转变。不同摩尔比的酶和抑制剂混合物的解折叠焓表明，相互作用焓比从荧光滴定法推导得出的值（上原，Y.，户村，B.，& 弘美，K.（1978年）《生物化学杂志》（东京）84卷，第1195 - 1202页）大得多。
