Dunn R V, Réat V, Finney J, Ferrand M, Smith J C, Daniel R M
Department of Biological Sciences, University of Waikato, Hamilton, New Zealand.
Biochem J. 2000 Mar 1;346 Pt 2(Pt 2):355-8.
The activity and dynamics of a simple, single subunit enzyme, the xylanase from Thermotoga maritima strain Fj SS3B.1 have been measured under similar conditions, from -70 to +10 degrees C. The internal motions of the enzyme, as evidenced by neutron scattering, undergo a sharp transition within this temperature range; they show no evidence for picosecond-timescale anharmonic behaviour (e.g. local diffusive motions or jumps between alternative conformations) at temperatures below -50 degrees C, whereas these motions are strongly activated at higher temperatures. The activity follows Arrhenius behaviour over the whole of the temperature range investigated, -70 to +10 degrees C. The results indicate that a temperature range exists over which the enzyme rate-limiting step is independent of fast anharmonic dynamics.
已在-70至+10摄氏度的相似条件下，测定了一种简单的单亚基酶——来自嗜热栖热菌菌株Fj SS3B.1的木聚糖酶的活性和动力学。中子散射证明，该酶的内部运动在此温度范围内经历了急剧转变；在低于-50摄氏度的温度下，没有证据表明其存在皮秒时间尺度的非谐行为（例如局部扩散运动或不同构象之间的跳跃），而在较高温度下这些运动被强烈激活。在所研究的整个温度范围-70至+10摄氏度内，活性遵循阿伦尼乌斯行为。结果表明，存在一个温度范围，在此范围内酶的限速步骤与快速非谐动力学无关。
