Isolation and Properties of Superoxide Dismutase from Ram Spermatozoa and Erythrocytes1

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Abstract
Mammalian spermatozoa are highly susceptible to oxygen-induced injury. Superoxide dismutase apparently serves a role in protecting cells, e.g., erythrocytes, against it. The content and properties of this enzyme in ejaculated ram spermatozoa were examined and compared with that in ram erythrocytes. Spermatozoa contained 30 units of activity/109 cells, an amount similar to that in erythrocytes. The enzyme was purified from both sources and shown to exhibit identical protein and activity staining on polyacrylamide gel electrophoresis, MW, subunit composition and UV absorption spectrum. Metal analysis showed 2 equivalents each of Cu and Zn/mole of protein. However, ram erythrocyte superoxide dismutase differed from that of other species in its high content of lysine and arginine. The specific activity of the enzyme in spermatozoa was about 10 times that in seminal plasma. The highest specific activity was found in cytoplasmic droplets. Comparison of superoxide dismutase, glutathione peroxidase and glutathione reductase activities in spermatozoa and erythrocytes indicated a much lower content of glutathione peroxidase in spermatozoa suggesting that ineffective H2O2 disposal forms the basis of the susceptibility of ram spermatozoa to oxygen toxicity.

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