Mammalian tyrosinase: Effect of ions on enzyme action

Abstract

1. 1. The univalent cations Li+, Na+, K+, and NH4+ have no effect on tyrosinase action.2. 2. The anions, fluoride, chloride, acetate, and oxalate, consistently inhibit the tyrosine-tyrosinase and dopa-tyrosinase reactions. Iodate, persulfate, and nitrite also inhibit these reactions. Relatively large amounts of these anions are required to produce inhibition.3. 3. Of 24 metal ions tested, only mercury, silver, and gold can produce an inactive enzyme preparation. The ions compete with copper ions for active centers on apotyrosinase. These competitive inhibition reactions are only slowly reversible.4. 4. No cations or anions accelerate tyrosinase action.5. 5. Copper ions are not bound to tyrosinase by a mercaptide linkage.