The influence of the reaction pH was evaluated by applying 70 mM Tris-HCl pH 7, 8 and 9. The following substrates were used: Urd: RK, dAMP: AMPK, CMP: (d)CMPK, GMP: GMPK, TMP: TMPK and UMP: UMPK. The reactions were preheated to 37 °C and started by the addition of diluted enzyme stock solution. After 5 min, a 30 µL sample was stopped with 780 µL cold deionized water and analyzed by the luminescent assay.