Is butyrylcholinesterase of the rat CNS a membrane-bound enzyme?

The study of Arrhenius plots for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity from the rat brain and spinal cord revealed that in contrast to AChE, which exhibited biphasic Arrhenius plots with a distinct break (transition temperature) at about 16-18 degrees C, BuChE showed no evidence of discontinuity and a higher activation energy in the physiological range of temperature. The results indicate lack of lipid-protein interaction in the case of BuChE of the CNS tissue. It is inferred that BuChE, in contrast to AChE, is not bound in any significant way to cellular membranes of the CNS tissue.