Having purified enzymes in hand, activity was determined at 37 °C using their putative natural nucleoside or nucleotide substrates. Phosphotransferase activity was confirmed for all enzymes except for TmNuc, TmUK and TmAsK. As nucleosides are not the natural substrates for nucleotidase, additional activity tests were performed with adenosine 5'-nucleotides, and phosphatase activity towards adenosine monophosphate (AMP) and adenosine diphosphate (ADP) was shown (data not shown). Hence, TmNuc is not able to phosphorylate nucleosides under the applied conditions.