Siddiqui Khawar Sohail, Bokhari Saleem Ahmed, Afzal Ahmed Jawaad, Singh Surjit
School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia.
IUBMB Life. 2004 Jul;56(7):403-7. doi: 10.1080/15216540400003052.
In most studies of enzyme kinetics it has been found sufficient to use the classical Transition State Theory (TST) of Eyring and others. This theory was based on the solvent being an ideal dilute substance treated as a heat bath. However, enzymes found in organisms adapted to very low (psychrophiles) and very high (thermophiles) temperatures are also subjected to variable solute concentrations and viscosities. Therefore, the TST may not always be applicable to enzyme reactions carried out in various solvents with viscosities ranging from moderate to very high. There have been numerous advances in the theory of chemical reactions in realistic non-ideal solvents such as Kramers Theory. In this paper we wish to propose a modified thermodynamic equation, which have contributions from kcat, Km and the viscosity of the medium in which the enzyme reaction is occurring. These could be very useful for determining the thermodynamics of enzymes catalyzing reactions at temperature extremes in the presence of substrate solutions of different compositions and viscosities.
在大多数酶动力学研究中，人们发现使用艾林等人的经典过渡态理论（TST）就足够了。该理论基于溶剂是一种被视为热浴的理想稀溶液。然而，在适应极低（嗜冷菌）和极高（嗜热菌）温度的生物体中发现的酶，也会受到可变溶质浓度和粘度的影响。因此，TST可能并不总是适用于在粘度范围从中等到非常高的各种溶剂中进行的酶反应。在诸如克莱默斯理论等现实非理想溶剂中的化学反应理论方面已经有了许多进展。在本文中，我们希望提出一个修正的热力学方程，该方程包含kcat、Km以及酶反应发生的介质粘度的贡献。这些对于确定在存在不同组成和粘度的底物溶液的极端温度下催化反应的酶的热力学可能非常有用。
