MOLECULAR PROPERTIES OF CHOLINE ACETYLTRANSFERASE FROM DIFFERENT SPECIES INVESTIGATED BY ISOELECTRIC FOCUSING AND ION EXCHANGE ADSORPTION

—The isoelectric point, surface charge and K_m for choline of choline acetyltransferase from different species were determined. Choline acetyltransferase from mouse and monkey brain was resolved into three molecular forms with isoelectric points at 7·1, 7·5, 8·4 and 7·0, 7·35, 8·35 respectively, whereas choline acetyltransferase from the electric organ of Torpedo and from rabbit brain showed a molecular form with isoelectric point 6·6 and 6·9, respectively. With the exception of rabbit brain enzyme, there was a good correlation between the isoelectric points and surface charges of the different choline acetyltransferases. The K_m's for choline were 0·66, 0·88, 0·92 and 3·5 mM for monkey, mouse, rabbit and Torpedo choline acetyltransferase respectively. The separated molecular forms of mouse and monkey enzymes did not show any significant difference in their affinity for choline.