Presence and Regional Distribution of Sialyl Transferase in the Epididymis of the Rat1

Epididymal tissue contains a glycoprotein-glycosyl transferase which transfers sialyl residues from cytidine 5′-monophosphate-sialic (CMP-sialic) to endogenous or exogenous (desialo-fetuin) acceptors. Extracts from caput epididymis have 15 times more activity than do extracts from cauda epididymis. Caput spermatozoa were as good sialyl acceptors as fetuin with caput homogenates, and better than fetuin with cauda homogenates. On the contrary, cauda spermatozoa behave as inhibitors of the enzymatic activity, particularly with caput extracts. No transferase activity could be detected in caput spermatozoa in the absence of epididymal extracts. On the contrary, cauda spermatozoa showed a small, but clear, transferase activity but were unacceptable as receptors.