Assays were performed in 5 and 10% of aprotic dipolar co-solvents, at 60°C, twelve units/ml cell lysate were added to 150 ml of a solution kept thermostatically at 60 °C, and having the following composition of substrate solutions:15mM Uridine/2 ' -Deoxyuridine,5 mM 2,6-Diaminopurine, and 30 mM potassium phosphate buffer, pH 7. After 5 hours, the reaction mixture was filtered by centrifugation at 2000 x g for 30 min, at 4°C, through an Amicon ultra-4 Centrifugal Filter Devices (Millipore, Bedford, MA) with a 3000-Da cutoff, and the filtrate was recovered.
