Developmental Differences Between Soluble and Membrane-Bound Fractions of Choline-O-Acetyltransferase in Neonatal Mouse Brain

Three fractions (one soluble and two membrane-bound) of choline acetyltransferase (ChAT) isolated from a nerve ending fraction of mouse forebrain, which have previously been reported to differ in several biochemical and physical aspects, were also found to differ in their rates of postnatal development. At 2 days of age, the activity in all three fractions was very low. Sodium phosphate buffer-soluble (cytoplasmic) ChAT activity increased significantly by 8 days of age, whereas the ChAT activity of the two membrane-bound fractions (NaCl- and Triton-soluble) did not increase until 13 days of age. These results suggested that the differences observed between the three fractions of ChAT prepared from mouse brain are not solely artifacts of the isolation procedure.