Interaction of Phosphates of the Acyclic Nucleoside Phosphonates with Nucleoside Diphosphate Kinase from Yeast and Bovine Liver

Abstract

The ability of monophosphates of selected acyclic nucleoside phosphonates to serve as substrates for the title NDP kinases was studied. Comparison of the kinetic constants (KM, Vmax, kcat and kcat/KM) estimates indicates that the yeast enzyme catalyzes the phosphorylation of purine and pyrimidine acyclic nucleoside phosphate phosphonates of the 9-[2-(phosphonomethoxy)ethyl] and/or 9-[2-(phosphonomethoxy)propyl] series more efficiently than bovine liver NDP kinase. Yeast enzyme preferentially phosphorylates phosphates of the (phosphono- methoxyalkyl)guanines rather than their adenine counterparts; both enzymes phosphorylate R-enantiomers of the 9-[2-(phosphonomethoxy)propyl] series more efficiently than the corresponding S-enantiomers. Substitution of the aliphatic chain at the position 3 with hydroxymethyl group considerably increases the substrate activity of phosphate of acyclic nucleoside phosphonate. The resulting substrate activity (kcat/KM ratio) of all acyclic nucleoside phosphonate phosphates studied is three to five orders of magnitude lower than that for natural NDPs.