Coordination Chemical Studies on Metalloenzymes I. Kinetics and Mechanism of the Zn(II) Exchange Reaction between Chelating Agent and Apo-Bovine Carbonic Anhydrase

Abstract
The mechanism of removal of the zinc ion from bovine carbonic anhydrase [EC 4. 2.1.1] (BCA) by a chelating agent was studied. It was shown that the removal of the zinc ion from BCA took place through the formation of a ternary complex involving the enzyme, chelating agent, and metal ions. The formation constant of the ternary complex (KEML) was 102 M−1. This value was lower than the formation constant assumed by Wilkins. The reaction of zinc-2, 6-pyridinedicarboxylate complex with the apoenzyme also took place through the formation of the ternary complex and the species which reacted with apo-BCA was a 1: 1 complex of zinc and 2, 6-pyridinedicarboxylate. The theoretical equilibrium equation derived from the reaction mechanism showed a good fit with observed equilibrium dialysis data.

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