Starch as a Polymer-Based Medium Modifier to Analyze Enzyme Activity under Conditions Close to Intracellular Media: Butyrylcholinesterase as a Model Enzyme

Abstract The study demonstrates the possibility of using starch to model macromolecular crowding and intracellular medium. A kinetic approach is used to reveal specific functioning of butyrylcholinesterases from different sources in the starch medium. In the study solutions, the Michaelis constant increases, indicating a decrease in the enzyme affinity for the substrate in the presence of the polymer. In the 9% starch solution, this parameter for butyrylcholinesterase from equine serum is 4.6 times higher than in the buffer solution, while the decrease in Vmax is not significant; Vmax values in most solutions are close to those in buffer solution. Model compounds—glycerol and sucrose—are used to impair diffusion control of the reaction studied. Inhibition mechanisms are retained in solutions with starch concentrations, ranging from 1 to 5%, whatever the inhibitor—chlorophos or neostigmine—is used.