Inhibition by styrylpyridines of purified rat and bovine brain choline acetyltransferase

Nine styrylpyridine analogs were tested as inhibitors of choline acetyltransferase which had been highly purified from rat cerebrum and bovine caudate nuclei. In general, concentrations required to achieve 50% inhibition (I50 values) were in the micromolar range. For some analogs, I50 values were similar to those obtained previously by other investigators who used less purified enzyme preparations. With certain analogs, however, the measured values of I50 changed as the transferase became more purified, which may indicate the presence in the extract of other molecules which can interact with the enzyme. The methods used in purification of the enzyme suggest that the molecule which modifies the activity of CAT is probably a protein. The mode of inhibition by naphthylvinylpyridinium was found to be uncompetitive with respect to both choline and acetyl coenzyme A for both the rat and bovine transferases.