Nucleotide stereochemistry in the formyltetrahydrofolate synthetase reaction

In a recent study, we have shown that N10-formyltetrahydrofolate synthetase prefers (Sp)-MgATP beta S over the Rp isomer in the forward reaction. In this report the stereochemistry of ATP beta S produced from prochiral ADP beta S in the reverse reaction was determined. The ATP beta S product was purified and tested as a substrate for hexokinase (preference for the Rp isomer), adenylate kinase (preference for the Sp isomer) and N10-formyltetrahydrofolate synthetase. A comparison of kinetic constants for the product and the authentic Sp and Rp isomers shows that the product is the Sp diastereomer. 31P NMR was also used to identify the product as (Sp)-ATP beta S.