Sialyl Transferase in Human Semen

The activity of the enzyme sialyl transferase, which is responsible for the transfer of sialic acid, has been examined in the following human seminal plasma: (1) originating from semen with sperm counts above 30 × 106/ml and exhibiting normal values of other andrological parameters; (2) from semen with sperm counts below 25 × 106/ml and with other andrological parameters of poor quality; (3) from semen devoid of sperm. Additionally, enzyme activity was examined in fractionated (split) semen. The activity in plasma based on measurement of radioactivity incorporated into asialofetuin, following incubation in the presence of 14C sialic acid, was expressed as cpm both per volume and per mg protein. There was a tendency for decreased activity with the decrease in sperm density of semen. The difference, however, lacked statistical significance. Enzyme activity in split semen was significantly lower in the first than in the second fraction.