An artificial phosphodiesterase (1) bearing two types of metal binding sites, a catalytic site and a regulatory bipyridine site showed a unique allosteric transition in the catalytic activity against the metal concentration. The rate constants for the hydrolysis reaction of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) and RNA dimer (ApA) with and without an effector metal ion were evaluated; the kobs value of HPNP hydrolysis for 1•(Zn 2+)3 (2.0 × 10-4 s-1) is 3.3 times larger than that for 1•(Zn2+)2. In the case of 1 and Cu2+, a 19.4 times larger kobs value was obtained for 1•(Cu2+)3 (1.2 × 10-3 s -1) against 1•(Cu2+)2. The increase in the catalytic activity is ascribed to the allosteric conformational transition of 1 induced by the coordination of effector metal ion to the Bpy moiety. A detailed investigation revealed that a conformational change of 1 induced by the third M2+ complexation enhances the rate of hydrolysis rather than a change in the substrate affinity.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry