Glutathione conjugation in male reproductive system: studies on glutathione-S-transferase of bull and boar epididymis.

Abstract

Male reproductive organs are extremely sensitive to the negative influence of toxic environmental factors as well as drugs, and until now not many attempts have been made at studying the detoxication enzymes and the relationship between the activity of those enzymes and spermatozoa fertility. In the present work we studied cytosolic glutathione-S-transferases (GST, EC 2.5.1.18) from different parts (head, corpus and tail) of bull and boar epididymis. We isolated two molecular forms of GST from each part of epididymis, characterized their biochemical properties and examined the mechanism of the catalyzed reaction. On the basis of their substrate specificity and isoelectric point, the isoforms were found to belong to the near neutral GST class mi. All examined GST forms exhibited higher affinity towards GSH than towards 1-chloro-2,4-dinitrobenzene (CDNB) and bull epididymis GST forms showed biphasic Lineweaver-Burk double reciprocal curves in the presence of GSH as a variable substrate. Boar epididymis anionic GST had the -SH groups both in the GSH and the CDNB binding place, whereas the cationic GST form--arginine residues in the CDNB binding place. Bull epididymis GST forms contained neither thiol nor arginine residues essential for catalytic activity.