Comparing the effects of organic cosolvents on acetylcholinesterase and butyrylcholinesterase activity.

The use of cosolvents to solubilize compounds under investigation while having minimal effects on enzyme activity is an important component in many biochemical studies. Predicting the effects of cosolvents on enzyme activity can be complicated, as enzymes with similar overall structures might exhibit different behaviors in different cosolvents. In this study, the effects of several commonly used cosolvents: Methanol, acetonitrile, acetone, and dimethyl sulfoxide (DMSO), on two cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), were evaluated. Although the overall structures are highly similar, AChE activity was more sensitive to the organic cosolvents tested compared to BChE. Effects of the cosolvents on activity did not vary over time and activity was restored upon dilution of the cosolvent. Michaelis-Menten kinetics experiments showed that V values were not substantially affected, while K values increased up to ∼20-fold for AChE and ∼4-fold for BChE in the presence of 5% DMSO or acetone. The results suggest that BChE demonstrates more robustness to its cosolvent environment compared to AChE, and that cosolvents effects may arise from the molecules acting as inhibitors. The results may aid decisions of cosolvents used in enzyme assays and may help guide experimental conditions and design when conducting experiments comparing different enzymes.