Recognition and catalytic hydrolysis of adenosine 5′-triphosphate by cadmium(II) and L-glutamic acid

Abstract

Interactions among Cd2+, glutamic acid (Glu), and adenosine 5′-triphosphate (ATP) have been studied by potentiometric pH titration, IR, Raman, fluorescence, and NMR methods. In the Cd2+–ATP binary system, the main interaction sites are the α-, β-, and γ-phosphate groups, N-1, and/or N-7. Cd2+ binds to the N-1 site at relatively low pH and binds to the N-7 site of adenosine ring of ATP with increasing pH. In the Cd2+–Glu–ATP ternary system, ATP mainly binds to Cd2+ by the triphosphate chain. Oxygens of Glu coordinate with Cd2+ to form a complex to catalyze ATP hydrolysis. Hydrolysis of ATP catalyzed by the CdGlu complex was studied at pH 7.0 and 80°C by 31P-NMR spectrometry. Kinetics studies showed that the rate constant of ATP hydrolysis was 0.0199 min−1 in the ternary system, which is 9.9-fold faster than that in the ATP solution (2.01 × 10−3 min−1). Hydrolysis occurs through an addition–elimination reaction mechanism with Cd2+ regulating the recognition and catalytic hydrolysis of ATP; water participates in the hydrolysis reaction of ATP at different steps with different functions in the ternary system.