Association and Dissociation of Bacillus subtilis α-Amylase Molecule:III. The Effects of pH and Salts on the Monomer-Dimer Transformation

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概要

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• 1. The change in the equilibrium between monomer and dimer of Bacillus subtilis α-amylase with pH from 6 to 9 was examined by the sedimentation velocity experiments. It was found that the slower moving com-ponent in the sedimentation pattern increases with increasing pH. 2. The monomer-dimer transformation of B. α-amylase was studied at various conditions by light scattering measurements. The value of Kc/R90 depended upon the protein con-centration. In 0.1M NaCl-0.005M calcium acetate, Kc/R90 was independent of the protein concentration when the protein concentration was more than 0.5%. The molecular weight calculated from the values of Kc/R90 in this region was found to be 97, 600, the molecular weight of the dimer. As the value of pH increases the equilibrium shifted toward the monomer. This was in accord with the results of the sedimentation measurements. Treat-ment with calcium-EDTA at pH 7.0, however, did not cause a perfect dissociation of the dimer into the monomer and the dimer remained slightly. 3. B. α-amylase treated with sodium-EDTA at pH 7.0 was studied by the Archibald method and by optical rotatory dispersion. For at least three days of the treatment, the inhomogeneity in the molecular weight was not observed and the molecular weight was found to be 48, 200. However, the optical rotatory dispersion constant decreased gradually during the incubation. 4. An attempt to analyze the light scat-tering data was made in order to evaluate the equilibrium constant between monomer and dimer. The equilibrium constant was estimated to be 2×109 mole-2 liter2. The authors would like to express their thanks to Nagase Sangyo Co., Ltd. and Daiwa Kasei Co., Ltd. for supplying Bacillus subtilis α-amylase.

• 社団法人 日本生化学会の論文

著者

• Isemura Toshizo

  Division of Physical Chemistry, Institute for Protein Research, Osaka University

• KAKIUCHI KINJI

  Division of Physical Chemistry, Institute for Protein Research, Osaka University

• HAMAGUCHI KOZO

  Division of Physical Chemistry, Institute for Protein Research, Osaka University

関連論文

• Steric Structure of L-Proline Oligopeptides. IV. Proton Magnetic Resonance Studies of L-Proline Oligopeptides
• Association and Dissociation of Bacillus subtilis α-Amylase Molecule:III. The Effects of pH and Salts on the Monomer-Dimer Transformation

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