A Calcium(II)-Based <Emphasis Type="SmallCaps">l</Emphasis>-Arginine for ATP Binding and Hydrolysis

The supramolecular recognition of Ca(II) and N _α-4-tosyl-l-arginine methyl ester hydrochloride (TAME) with ATP were investigated using ¹H and ³¹P NMR spectra. In the Ca(II)–ATP–TAME ternary system, Ca²⁺ and TAME bind with ATP via the phosphate chain and adenine ring of ATP. The binding forces are mainly electrostatic and cation (Ca²⁺)–π and π–π stacking interaction. Furthermore, the hydrolysis of ATP catalyzed by Ca(II) and TAME was studied at pH 7.0 and 60 °C using ³¹P NMR spectra. Kinetics studies show that the ATP hydrolysis rate constant is 0.1035 h⁻¹ in the Ca(II)–TAME–ATP ternary system, whereas the value is 8.5 × 10⁻³ h⁻¹ under the same conditions without TAME and Ca²⁺. The Ca(II) ions and TAME accelerate the ATP hydrolysis process about 12-fold. The proposed mechanism of ATP hydrolysis catalyzed by Ca²⁺–TAME occurs through an addition–elimination reaction sequence. These results can help us get more useful information at the molecular level about the key amino acid residue(s) and metal ions that serve as cofactors in the ATPase effect on ATP hydrolysis/synthesis.