A separate catalase and peroxidase in sea urchin sperm

The release of hydrogen peroxide (H₂O₂) by the fertilized sea urchin egg has been shown to assist in the prevention of polyspermy [Coburn et al, 1981; Boldt et al, 1981]. Physiological data suggested that egg‐derived H₂O₂ reacts with a phenylhydrazine‐sensitive sperm peroxidase to inactivate sperm, while a 3‐amino‐1,2,4‐triazole‐sensitive catalase acts to protect sperm from H₂O₂ [Boldt et al, 1981]. Strongylocentrotus purpuratus sperm contain heat and pronase labile catalase and peroxidase activities. Differential extraction of sperm (hypotonic phosphate buffer for catalase and Triton X‐100 at high ionic strength for peroxidase) results in complete separation of these enzyme activities. The catalase is highly sensitive to inhibition by azide and 3‐amino‐1,2,4‐triazole, and less sensitive to inhibition by phenylhydrazine. The peroxidase is highly sensitive to inhibition by phenylhydrazine and relatively insensitive to 3‐amino‐1,2,4‐triazole and azide. These results show that two distinct H₂O₂ reactive enzymes, catalase and peroxidase, are present in sea urchin sperm, and are consistent with our hypothesis concerning the biological functions of these enzymes in fertilization.