In contrast to TmPPDK, TmPK and TmAcK accepted all natural ribo-and deoxyriboNDPs (Figure ). While TmPK showed a preference for purine NDPs, TmAcK converted all NDPs with comparable high conversion. Our results fit well to the observation that TmAcK accepts ATP, GTP, ITP, UTP and CTP as phosphate donors for acetyl phosphate synthesis . PKs and AcKs are well known to show a wide substrate scope with PK and AcK of Geobacillus stearothermophilus being good examples. GsPK was described to accept all natural riboNDPs ADP, GDP, IDP, UDP and CDP, with the latter being the worst substrate . GsAcK was studied in the direction of acetyl phosphate synthesis and ATP, GTP, UTP and CTP were shown to serve as phosphate donors . Purine NTPs were preferred over pyrimidine NTPs.