酶反应过程中的体积变化。压力对转化酶、葡聚糖酶和葡糖转移酶作用的影响。

Volume changes during enzyme reactions. The influence of pressure on the action of invertase, dextranase and dextransucrase.

作者信息

Ludwig H, Greulich K O

出版信息

Biophys Chem. 1978 May;8(2):163-9. doi: 10.1016/0301-4622(78)80007-6.

Abstract

The pressure dependence of the maximum velocities and the Michaelis constants for the enzymes invertase and dextranase was measured up to 1400 bar. The corresponding activation volumes deltaV not equal to c and deltaV not equal to Km proved to be independent of pressure. Together with data from other sources the meaning of deltaV not equal to c and deltaV not equal to Km is established and the volume profiles of the reactions are constructed. These profiles are similar in contour to the volume profile of the dextran formation catalyzed by the enzyme dextransucrase, but the amount of the volume changes is very much larger for dextransucrase. The evaluation of salt effects shows, that for all three enzymes solvent interactions are not important in explaining the results. The reaction mechanisms seem to be governed by conformation changes of the enzymes. The larger effects in dextransucrase are explained by the produced dextran chain remaining tightly bound to the enzyme and being transported relative to the enzymes position in each reaction cycle.

摘要

测定了转化酶和右旋糖酐酶的最大反应速度及米氏常数随压力的变化关系，压力范围高达1400巴。结果表明，相应的活化体积ΔV≠c和ΔV≠Km与压力无关。结合其他来源的数据，确定了ΔV≠c和ΔV≠Km的意义，并构建了反应的体积剖面图。这些剖面图在轮廓上与由右旋糖酐蔗糖酶催化的右旋糖酐形成的体积剖面图相似，但右旋糖酐蔗糖酶的体积变化量要大得多。盐效应的评估表明，对于所有这三种酶来说，溶剂相互作用对结果的解释并不重要。反应机制似乎受酶的构象变化支配。右旋糖酐蔗糖酶中较大的效应可解释为所产生的右旋糖酐链紧密结合在酶上，并在每个反应循环中相对于酶的位置发生移动。