| Abstract: | —The rates of acetylation of choline and the mono-, di-, and tri-ethyl analogues of choline by choline acetyltransferase (acetyl-CoA: choline O-acetyltransferase; EC 2.3.1.6) were studied with a partially purified enzyme from bovine caudate nucleus. All the substrates were acetylated by ChAc. The rates of acetylation at low concentrations of substrate were choline >MEC >DEC >TEC, but at high concentrations MEC was acetylated more rapidly than choline. These results have been compared to those of previous workers. The mode of binding of choline and its analogues to ChAc is discussed, and it is suggested that replacement of methyl by ethyl groups results in a lower energy of binding of the substrate to the active site of the enzyme. |
