TWO FRACTIONS OF SPECIFIC CHOLINESTERASE PRESENT IN HOMOGENIZED NORMAL MOUSE BRAIN

Abstract

When mouse brain was ho-mogenized in a buffer soln. and centrifuged it was found that 82.9% of the total cholinesterase activity was in the supernatant fluid and 16.8% was in the residue. The distribution between supernatant fluid and residue was found to be dependent on the NaCl concn. and the pH of the homogenate. When the NaCl concn. of a distilled water homogenate, in which all of the activity is in the supernatant, was varied prior to centrifuging, maximal residue activity was reached with a concn. of 0.075 [image] NaCl. When the pH of a 0.15 [image] NaCl homogenate was varied between 7.5 and 10 there was a further increase in the residue cholinesterase activity. The distribution of the activity was not dependent upon the presence of intact cells, and therefore could not be due to the presence of intra- and extra-cellular fractions. The pH optima of the 2 fractions were the same. There was no difference in the relative activities of the 2 fractions towards acetyl-beta-methylcholine, propionylcholine, butyrylcholine, benzoylcholine and ethyl butyrate. Upon heating the fractions at 54 C, the precipitated fraction was considerably more heat labile than the supernatant fraction. It appears that the heat inactivation of the precipitated fraction is a 2d order reaction.