Temperature effects on cholinesterases from rat brain capillaries.

The activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in rat brain capillaries were measured as a function of temperature. Arrhenius plots of the data revealed that AChE exhibits a biphasic Arrhenius plot with a distinct break (transition temperature) at about 15.2 kcal/mol. In contrast, BuChE did not show evidence of discontinuity. BuChE showed an activation energy higher than that of AChE in the physiological range of temperature. These data suggest a lack of lipid-protein interaction in the case of BuChE. Although the possibility exists that BuChE is weakly anchored to the membranes, our results indicate that BuChE is not bound, at least significantly, to cellular membranes in brain capillaries as is AChE.