The application of a simple, sensitive disc assay for sialyltransferase activity to particulate and soluble enzyme preparations and its use in measuring enzymatic activity in human plasma samples.

A simple assay for the determination of sialyltransferase activity is described. The method involves the isolation of the radioactive reaction product on cellulose paper discs washed with trichloroacetic acid, thereby greatly facilitating the handling of large numbers of assays. This procedure is both more accurate and more sensitive than that involving precipitation with protein denaturants and separation by centrifugation, and is applicable to both soluble and particulate enzyme preparations. The application of the method to the determination of sialytransferase in human plasma is detailed. Enzyme activity is elevated two-fold in both cancer patients and patients with non-malignant disease. This suggests that the diagnostic use of determinations of sialyltransferase activity may be limited by its non-specificity.