Dirofilaria immitis: a large-scale purification method and partial characteristics of a superoxide dismutase from adult worms.

A superoxide dismutase (SOD) from adult worms of Dirofilaria immitis was purified using ethanol-chloroform and acetone treatment, DE 52 cellulose, and Sephadex G-75 gel chromatography to obtain a 677-fold purification and a specific activity of 5483 units/mg of protein. The purified SOD was essentially homogeneous as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and composed of two identical 18.5 kDa subunits. The purified SOD was inactivated completely by 3 mM potassium cyanide, and reduced to about 18% of the initial activity by incubation at 100 degrees C for 10 min and to 28% by treatment with 2% SDS. This means that D. immitis SOD differs markedly from the mammalian Cu/Zn SOD, although it is indeed a Cu/Zn SOD. Atomic absorption spectrometry revealed the presence of 0.80 mole of Cu and 0.78 mole of Zn per mole of subunit. The enzyme consisted of 22.6% acidic and 11.9% basic amino acids. No free amino acid was detected in the SOD by N-terminal amino acid sequencing.