HsdCK was chosen as biocatalyst to validate the established approach in comparison to reactions which were pipetted manually. Kinase reactions were performed with natural (deoxy)nucleosides that were well accepted by HsdCK before (Figure , dAdo, dGuo, Cyd, dCyd, and Thd). The results of the semiautomated assay were in good accordance to manually pipetted reactions for all substrates tested (Figure ). Activities with purine (B) and pyrimidine (C) nucleoside substrates were determined for the chosen NKs using standard screening conditions. If a discrepancy to literature data was observed, assay conditions were optimized: 0.004 U DmdNK were applied, 0.0012 U TK were used, HsAK reactions including 50 mM KCl and 0.004 U enzyme (see also Figure ). Substrates were only presented if conversions > 10 % were observed. Please see Table for the conversions. Ado: adenosine, dAdo: 2'-deoxyadenosine, Guo: guanosine, dGuo: In literature, DmdNK and HsdCK were described as wide-spectrum enzymes. Indeed, both enzymes available for HsdCK or DmdNK , an activity towards a few substrates was not known before.