Peroxidase activities in bull spermatozoa

The present study was carried out to determine the localization of peroxidase activity in bull spermatozoa. 3,3′‐Diaminobenzidine (DAB) was used as a substrate for revealing peroxidase activity, and light and electron microscopic analysis of the results obtained was performed. Peroxidase activity was detected in the mitochondria of the middle piece and the outer acrosomal membrane. Catalase was excluded as an enzyme, catalyzing the detected peroxidase activity. Concerning the biochemical properties of bull sperm peroxidases, peroxidase activity was found to be manifested in a large pH range, 4–10.5. Bull sperm peroxidase activity appeared to be temperature sensitive and azide sensitive and could be readily inhibited by phenylhydrazine. Electrophoretic analysis of the proteins from bull sperm extracts separated in a Davis‐Ornstein system of 7% polyacrylamide gel, followed by the determination of peroxidase activity on the polyacrylamide gels, revealed that all 14 sperm protein fractions available on the gel possessed peroxidase when benzidine was used as a substrate. The possible reasons for the electrophoretic heterogeneity of bull sperm peroxidases are discussed. © 1994 Wiley‐Liss, Inc.