Biological Role of Glutathione S-Transferases on Sperm

Abstract

Our earlier studies reported the identification of a rat testicular protein of 24 kDa size with significant similarity at the NH₂-terminus with Mu class glutathione S-transferases (GST)* In this study, we describe our observations on the presence of GSTs on goat spermatozoa and their possible functional role in sperm physiology. Both GST-Pi and Mu are detectable on goat sperm surface at distinct cellular domains. Selective inhibition of Pi class GST by the Pi specific antisera or Mu GSTs by Mu specific antisera reduces fertilization rates and the rate of acrosome reaction. Enzymatic activity of GSP1 or live spermatozoa is not inhibited by the two antisera. The inability of the antibodies to do so indicate that the reduction in fertilization rates and acrosome reaction caused by the antibodies is through a mechanism which does not interfere with the catalytic activity of the molecule. We also describe interference with normal motility, acrosome reaction and fertilizing ability of the goat sperm at inhibition of GST activity. That these functional impairments are due to membrane changes is evident from the increase in the number of membrane damaged sperm and changes in the lipid peroxidation status of these cells after GST inhibitor treatment. The data argues for a role of GST in multiple fertility related events.