Epididymal a-L-fucosidase and its possible role in remodelling the surface of bull spermatozoa

Abstract

The mammalian epididymis provides an appropriate environment for sperm maturation. During theepididymal transit, spermatozoa undergo biochemical and morphological changes that lead to theacquisition of the fertilizing capacity. In this study we analysed the fucosylation status of membraneglycoproteins in the spermatozoa obtained from different regions of the bull epididymis. High amountsof fucose were detected on caput spermatozoa (R.F.I. ¼ 1010 ± 20.35), mostly located in the postacrosomezone. A significant decrease in the fucose levels was detected toward the cauda(R.F.I. ¼ 540.5 ± 49.93) (P < 0.05). This decrease was in line with the increased activity of a-L-fucosidasein the cauda fluid. In sperm from the cauda, the defucosylation occurred in some proteins, whereasothers showed higher fucosylation rates. A significant decrease of fucose in the gametes was observedupon incubation of crude cauda fluid with caput spermatozoa (from R.F.I. ¼ 1.45 ± 0.08 to 1.06 ± 0.03)(P < 0.05) indicating that the a-L-fucosidase present in the epididymal fluid is active on spermatozoa.Moreover, this effect was blocked with specific enzyme inhibitors. These results provide direct evidencethat the a-L-fucosidase from epididymal fluid participates in the fucose removal from spermatozoa, as astep of sperm maturation in the bull epididymis.