title: Inhibition of cobalt(II) carboxypeptidase A by ligands. Kinetic evidence for the formation of a ternary enzyme-metal-ligand complex.
abstract: Saturation kinetics are observed in the inhibition of cobalt carboxypeptidase A by the chelating agent 1,10-phenanthroline. The association constant K1 for the formation of the enzyme-metal-ligand ternary complex and k2, the rate of breakup of the ternary complex, have been obtained. A mechanism is proposed to account for the pH profile of the reaction which, in conjunction with K1, permits the calculation of the individual rate constants k1, k-1, k2, k3. The magnitude of the rate constant k1 suggests that cobalt(II) in CoCPA is five-coordinate. Similar but less extensive studies on inhibition by 2,2'-bipyridyl and 8-hydroquinoline-5-sulfonic acid have also been carried out.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors*; D043422:Carboxypeptidases A; D002417:Cattle; D003035:Cobalt / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008433:Mathematics; D010179:Pancreas / Q000201:enzymology; D011485:Protein Binding
chemical_list: D008024:Ligands; D003035:Cobalt; D002268:Carboxypeptidases; D043422:Carboxypeptidases A