Cytosol fraction was isolated from cat brain, and cytosolic Cu, Zn-superoxide dismutase (EC 1.15.1.1, SOD) was purified by ammonium sulfate precipitation, DEAE-Trisacryl M column chromatography, CM-Trisacryl M column chromatography and Sephadex G-100 gel filtration, and some physical properties of the purified enzyme was studied.
The results were summarized as follows:
1. Cat brain cytosolic Cu, Zn-SOD contained two isozymes.
2. The cytosolic Cu, Zn-SOD was purified approximately 206 fold.
3. The molecular weight of purified enzymes was estimated to be 34Kd by both Sephadex G-100 gel filtration and HPLC, and 17Kd by SDS-PAGE. This finding indicated that the enzyme is composed of´ two subunits of equal size, which were not covalently joined.
4. The activity of purified enzymes increased to 2.3 (in SOD isozyme I) and 4.5 (in SOD isozyme lI) times more active when the buffer pH raised from 7.8 to 10.0.
5. Azide at the concentration of 10mM inhibited the activity of purified enzymes by 40.4% (in SOD isozyme I) and 37.5% (in SOD isozyme II), respectively.
6. The activity of purified enzymes was inhibited 100% by 3mM (in SOD isozyme I) and 2mM concentration (in SOD isozyme II) of cyanide, respectively.
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