Jul 1, 1979

Kinetics of interaction of ligands with carboxypeptidase A

Journal of Inorganic Biochemistry
E J Billo

Abstract

Rate constants for the interaction of a number of ligands with the active site zinc ion of carboxypeptidase A have been measured at pH 7.0, 25 degrees, 1.0 M NaCl. Polydentate ligands such as EDTA, NTA or CyDta do not accelerate the rate at which the zinc ion dissociates from the protein. Bidentate or tridentate ligands on the other hand are able to attack the zinc ion directly; the rates are first order in enzyme and first order in ligand. A mechanism for the reaction is proposed, in which a ternary complex LZnCPA is formed which rapidly dissociates into ZnL and apo CPA. Comparison of results for a variety of ligands leads to the conclusion that in the ternary complex tridentate ligands bind to the zinc ion through only two donor groups. The reaction of 1.10-phenanthroline with ZnCPA has been studied from pH 6 to 9, and a mechanism proposed which accounts for the pH profile of the reaction.

  • References3
  • Citations10

Mentioned in this Paper

CPA1
Carboxypeptidase A
Carboxypeptidase A Activity
Edetic Acid, Sodium Salt
Zinc
Sodium Chloride
Carboxypeptidase
PH Profile Measurement
Ligands Activity
Edetic Acid

About this Paper

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