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A Novel Thermodynamic Relationship Based on Kramers Theory for Studying Enzyme Kinetics under High Viscosity
Author(s) -
Siddiqui Khawar Sohail,
Bokhari Saleem Ahmed,
Afzal Ahmed Jawaad,
Singh Surjit
Publication year - 2004
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216540400003052
Subject(s) - thermodynamics , enzyme kinetics , kinetics , viscosity , chemistry , solvent , substrate (aquarium) , psychrophile , transition state theory , enzyme , reaction rate constant , organic chemistry , physics , active site , classical mechanics , oceanography , geology
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. IUBMB Life, 56: 403‐407, 2004