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

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 V_max is not significant; V_max 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.