Activity of yeast orotidine-5 '-phosphate decarboxylase in the absence of metals

Yeast orotidine-5'-phosphate decarboxylase was recently shown to contain zi nc and to be inhibited by zinc-complexing agents. When the gene for the yea st enzyme was expressed in Escherichia coli, the gene product was devoid of metal atoms but exhibited a specific activity and molecular mass similar t o those of the enzyme obtained directly from yeast. This invalidates the hy pothesis that zinc is involved in substrate decarboxylation. The zinc-free enzyme undergoes thermal inactivation at a somewhat lower temperature than does the zinc-containing enzyme isolated from yeast.