Binding of beta-galactosidase from rat epididymal fluid to the sperm surface by high-affinity sites different from phosphomannosyl receptors.
beta-Galactosidase, known to be secreted by epithelial cells lining the rat epididymal duct, binds to the surface of spermatozoa from the caudal region with high affinity and in a saturable form. The binding was not inhibited by mannose-6-phosphate, but was inhibited by fructose phosphate derivatives, a peculiarity previously demonstrated for the membranes of epididymal tissue. Fructose phosphate derivatives released 55% of beta-galactosidase activity from the spermatozoa. These results suggest that in the epididymis there is a special transport system for hydrolases, which could be involved in the secretion of enzymes destined for spermatozoa. This transport would require receptors that recognize sugar ligands other than mannose-6-phosphate. These receptors were present in the epididymal tissue and on the sperm surface.
Sosa
M A
MA
Instituto de Histología y Embriología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-C.C. 56, Mendoza, Argentina.
Barbieri
M A
MA
Bertini
F
F
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004822:Epididymis / Q000201:enzymology*; D005636:Fructosephosphates / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013094:Spermatozoa / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism*
D005636:Fructosephosphates; C027618:fructose-6-phosphate; D001616:beta-Galactosidase