TmPPDK only converted AMP and dAMP to the respective NTPs with (d)ADP formed as byproducts to a lower percentage (Figure ). Additionally, it was shown that (d)ADP and (d)GDP were substrates of TmPPDK with comparable efficiency (Figure ). In good agreement with our results, TmPPDK was described before to be highly specific for AMP when tested with ribonucleotide monophosphates . However, little information is available on the substrate scope of PPDKs since mainly reactions with AMP as substrate were reported. For Clostridium symbiosum PPDK (CsPPDK) even an inhibitory effect of other NMPs like GMP and IMP was shown .