Metal coordination geometry of ternary complex between cobalt-bovine carbonic anhydrase and multidentate ligands.
Interaction of cobalt(II) bovine carbonic anhydrase with 3- and 4-pyridinecarboxylates, 2-pyridinecarboxylate, and 2,6-pyridinedicarboxylate has been investigated by the spectrophotometric method. The apparent formation constant of the ternary complex (ligand : cobalt ion : apoenzyme = 1 : 1 : 1) was determined from spectral data. The spectroscopic data of the ternary complex indicate that the 3- or 4-pyridinecarboxylate adduct has a five-coordination geometry through three donor atoms of the protein part of the enzyme, the carboxyl group of 3- or 4-pyridinecarboxylate, and a water molecule. 3- or 4-Pyridinecarboxylate behaves as a monodentate ligand. The spectrum of the ternary complex of 2-pyridinecarboxylate was very different from that of 3- or 4-pyridinecarboxylate. The spectra data indicate that 2-pyridinecarboxylate adduct has a five-coordination geometry and that it behaves as a bidentate ligand. The ternary complex of 2,6-pyridinedicarboxylate was so unstable that the spectrum of the ternary complex was determined by the indirect method. The spectrum of 2,6-pyridinedicarboxylate adduct shows lower molar absorption than that of 2-pyridinecarboxylate adduct. This result indicates that 2,6-pyridine dicarboxylate behaves possibly as a tridentate ligand.
D000818:Animals; D002257:Carbonic Anhydrase Inhibitors; D002256:Carbonic Anhydrases / Q000032:analysis*; D002417:Cattle; D002614:Chelating Agents; D055598:Chemical Phenomena; D002621:Chemistry; D003035:Cobalt / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007539:Isonicotinic Acids / Q000032:analysis; D008024:Ligands; D008433:Mathematics; D009539:Nicotinic Acids / Q000032:analysis; D010848:Picolinic Acids / Q000032:analysis; D013057:Spectrum Analysis
D002257:Carbonic Anhydrase Inhibitors; D002614:Chelating Agents; D007539:Isonicotinic Acids; D008024:Ligands; D009539:Nicotinic Acids; D010848:Picolinic Acids; D003035:Cobalt; D002256:Carbonic Anhydrases