The extraction and properties of superoxide dismutase from porcine blood

Crude Superoxide dismutase (SOD) was prepared by extraction with chloroform-ethanol, centrifugation and acetone precipitation. The specific activity of the SOD was 1570 units mg(-1), and an unusual ultraviolet spectrum with maximum absorbance at 256.4 nm was observed. When the SOD was kept at 40, 50 and 60 °C for 10 min, it showed little loss of stability but it retained only 95, 69, 45 and 2.5% of its original activity after holding at 60, 70, 75, and 80 °C for 5 min., respectively. When cupric ions were added, the thermostability of SOD was enhanced. When the extracted SOD was kept at -23, 4, 25 and 30 °C for 20 weeks, the relative activity retained was 76, 67, 26 and 16%, respectively. Using the sensitive test with cyanide and hydrogen peroxide, the acrylamide gel of the SOD showed this enzyme was of the Cu Zn type. The molecular weights of the holoenzyme and its subunits, estimated by SDS-polyacrylamide gel electrophoresis, were approximately 31 and 15 kD, respectively.