Fried Stephen D, Bagchi Sayan, Boxer Steven G
Department of Chemistry, Stanford University, Stanford, CA 94305-1052, USA.
Science. 2014 Dec 19;346(6216):1510-4. doi: 10.1126/science.1259802.
Enzymes use protein architecture to impose specific electrostatic fields onto their bound substrates, but the magnitude and catalytic effect of these electric fields have proven difficult to quantify with standard experimental approaches. Using vibrational Stark effect spectroscopy, we found that the active site of the enzyme ketosteroid isomerase (KSI) exerts an extremely large electric field onto the C=O chemical bond that undergoes a charge rearrangement in KSI's rate-determining step. Moreover, we found that the magnitude of the electric field exerted by the active site strongly correlates with the enzyme's catalytic rate enhancement, enabling us to quantify the fraction of the catalytic effect that is electrostatic in origin. The measurements described here may help explain the role of electrostatics in many other enzymes and biomolecular systems.
酶利用蛋白质结构将特定的静电场施加到其结合的底物上，但这些电场的大小和催化作用已证明难以用标准实验方法进行量化。利用振动斯塔克效应光谱，我们发现酮甾类异构酶（KSI）的活性位点对C=O化学键施加了一个极大的电场，该化学键在KSI的速率决定步骤中发生电荷重排。此外，我们发现活性位点施加的电场大小与酶的催化速率增强密切相关，这使我们能够量化源于静电的催化作用部分。此处描述的测量结果可能有助于解释静电在许多其他酶和生物分子系统中的作用。
