Edman L, Rigler R
Department of Medical Biophysics, Karolinska Institute, 171 77 Stockholm, Sweden.
Proc Natl Acad Sci U S A. 2000 Jul 18;97(15):8266-71. doi: 10.1073/pnas.130589397.
Immobilized single horseradish peroxidase enzymes were observed by confocal fluorescence spectroscopy during catalysis of the oxidation reaction of the nonfluorescent dihydrorhodamine 6G substrate into the highly fluorescent product rhodamine 6G. By extracting only the non-Markovian behavior of the spectroscopic two-state process of enzyme-product complex formation and release, memory landscapes were generated for single-enzyme molecules. The memory landscapes can be used to discriminate between different origins of stretched exponential kinetics that are found in the first-order correlation analysis. Memory landscapes of single-enzyme data shows oscillations that are expected in a single-enzyme system that possesses a set of transient states. Alternative origins of the oscillations may not, however, be ruled out. The data and analysis indicate that substrate interaction with the enzyme selects a set of conformational substates for which the enzyme is active.
在将非荧光二氢罗丹明6G底物催化氧化为高荧光产物罗丹明6G的过程中，通过共聚焦荧光光谱观察了固定化的单辣根过氧化物酶。通过仅提取酶-产物复合物形成和释放的光谱双态过程的非马尔可夫行为，生成了单酶分子的记忆景观。记忆景观可用于区分一级相关分析中发现的拉伸指数动力学的不同起源。单酶数据的记忆景观显示出在具有一组瞬态的单酶系统中预期的振荡。然而，振荡的其他起源不能排除。数据和分析表明，底物与酶的相互作用选择了一组酶具有活性的构象亚态。
