title: The role of zinc in the stabilization of the dimeric form of bacterial alpha-amylase.
abstract: Bacterial alpha-amylase was shown by equilibrium and velocity-sedimentation studies to be a monomer-dimer equilibrium system in 0.10M-NaCl/0.015M-calcium acetate/0.010M-EDTA, pH7.0; an association constant of 2.4 X 10(3)M-1 is obtained. Studies of the binding of Zn2+ to alpha-amylase in 0.10M-NaCl/0.005M-calcium acetate, pH7.0, yielded binding curves that exhibit dependence on the concentration of alpha-amylase (Zn2+-free) used in the equilibrium-dialysis experiments. Results are described very satisfactorily by a reaction scheme in which Zn2+ binds exclusively to the dimer of the above monomer--dimer system with an association constant of 1.0 X 10(6)M-1. The present results refute the earlier scheme for dimer stabilization by Zn2+ in which the metal ion formed a cross-link between two non polymerizing monomer units.
mesh_terms: D000681:Amylases; D002499:Centrifugation, Density Gradient; D055598:Chemical Phenomena; D002621:Chemistry; D003956:Dialysis; D004492:Edetic Acid; D046911:Macromolecular Substances; D015032:Zinc; D000516:alpha-Amylases
chemical_list: D046911:Macromolecular Substances; D004492:Edetic Acid; D000681:Amylases; D000516:alpha-Amylases; D015032:Zinc