title: Interaction of cobalt ions with carboxypeptidase A.
abstract: The interaction of cobalt(II) with native and cobalt(II)-substituted carboxypeptidase has been investigated, at pH 7.5, by electronic absorption and 1H NMR spectroscopies. The reaction of the cobalt(II) uptake by the metalloenzyme [MCPA] (M = Zn or Co) occurs very slowly and a bimetallic complex, [MCPA(Co)], is formed. On the basis of the 1H NOE experiments, the isotropically shifted proton resonances were assigned as belonging to a coordinated histidine residue. 1H NMR titrations of [ZnCPA(Co)] with zinc(II) show that the zinc ion does not compete with cobalt for binding to the noncatalytic site. The temperature dependence of the isotropic shifts, molar absorbance, and longitudinal relaxation time values are indicative of a five-coordinated geometry for the cobalt ion. The identification of the noncatalytic cobalt binding site is also discussed.
authors.affiliation: Department of Inorganic Chemistry, University of Valencia, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Moratal
authors.forename: J
authors.initials: J
authors.lastname: Castells
authors.forename: A
authors.initials: A
authors.lastname: Donaire
authors.forename: J
authors.initials: J
authors.lastname: Salgado
authors.forename: H R
authors.initials: HR
authors.lastname: Jiménez
authors.forename: R
authors.initials: R
authors.lastname: Domingo
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002268:Carboxypeptidases / Q000737:chemistry / Q000378:metabolism*; D043422:Carboxypeptidases A; D002417:Cattle; D003035:Cobalt / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013057:Spectrum Analysis; D015032:Zinc / Q000378:metabolism
chemical_list: D003035:Cobalt; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D015032:Zinc