Purification and Characterization of the Decarboxylase AMDase

To clarify the characteristics of AMDase, the effects of additives were examined. The addition of ATP and coenzyme A (CoA) to the enzyme reaction mixture did not enhance the rate of decarboxylation. In the case of malonyl-CoA decarboxylase, ATP and substrate form a mixed anhydride, which in turn reacts with CoA to form a thiol ester of the substrate. In the case of AMDase, however, neither ATP nor CoA had any effect, so this mechanism is unlikely. It is well established that avidin is a potent inhibitor of biotin-enzyme complex formation [11,12]. In this case, addition of avidin had no influence on decarboxylase activity, indicating that AMDase is not a biotin-dependent decarboxylase. Thus, the cofactor requirements of AMDase are entirely different from known analogous enzymes, such as malonyl-CoA decarboxylases. 

In contrast, a strong inhibitory effect of sulfhydryl reagents, including HgCl, HgCl, AgNOg, iodoacetate, and p-chloromercuribenzoate, was found. Thus, AMDase is a thiol decarboxylase. The activity of the enzyme was not lost upon incubation with 

---