Microsomal and plasma membrane sialyltransferase activity in rat epididymis.
3H-sialyl residues transfer by subcellular epididymal fractions [plasma membrane (PM), microsomes (MI), and mitochondria (MT)] to both endogenous and exogenous acceptors was studied. Their fraction purity was valued (5' nucleotidase and glucose 6-phosphatase activities). The glycoprotein or glycolipid N-acetyl neuraminyl transferase activity in microsomes were 5 times higher in caput than in cauda (624 to 125 pmoles/30 min/mg protein). PM activity also was higher in caput. In MT fraction, the activity was smaller. Two mechanisms related to spermatozoa glycoprotein changes during maturation are proposed: secretion to the lumen of molecules previously glycosilated in microsomes and transialylation to spermatozoa from membranal ectoenzymes localized on the surface of the epididymal epithelium.
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D004822:Epididymis / Q000201:enzymology*; D008297:Male; D008861:Microsomes / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D012799:Sialyltransferases / Q000378:metabolism*; D014018:Tissue Distribution; D014166:Transferases / Q000378:metabolism*
D014166:Transferases; D012799:Sialyltransferases