Arrhenius Analysis of the Electrophorus Electricus Acetylcholinesterase-Catalyzed Hydrolysis of Acetylthiocholine

Ellman's method was used to determine the Michaelis-Menten parameters for the hydrolysis of acetylthiocholine by Electrophorus electricus acetylcholinesterase from 12 to 37°C. Arrhenius analysis revealed that the activation energy for formation of the enzyme / substrate complex is 22.2 ± 1.1 kJ / mole. The Arrhenius plot of kcat is markedly curved and attributed to comparable rates of acylation and deacylation due to the absence of evidence for a temperature-dependent enzyme conformational change by differential scanning calorimetry.