The effect of the experimental antitumor agent caracemide on brain choline acetyltransferase

Caracemide was found to inhibit choline acetyltransferase (CAT) from rat brain. A concentration of 0.5 mM caracemide inhibited the enzyme by 93%, whereas a degradation product from caracemide, N‐(methycarbamoyloxy)acetamide, produced only a 50% inhibition. Two other degration products, N(methyl‐carbamoyloxy)‐N′‐methylurea and N‐hydroxy‐N′‐methlurea, lacked any inhibitory activity. With bovine brain CAT, caracemide showed noncompetitive inhibitio with the substrate choline, Km337 μM, KiμM, Vmax2.83 nmol acetylcholine fromed/ mg/mg protein and mixed inhibition with the substrate acetyl‐CoA, Km21 μM, Ki146 μM, Vmax3.85 noml acetylcholine formed/min/mg porotein.