Zinc solid-state NMR spectroscopy of human carbonic anhydrase: implications for the enzymatic mechanism
| Autor: | Andrew S. Lipton, Robert W. Heck, Paul D. Ellis |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Stereochemistry
Ab initio chemistry.chemical_element Zinc Biochemistry Catalysis chemistry.chemical_compound Colloid and Surface Chemistry Carbonic anhydrase Humans Nuclear Magnetic Resonance Biomolecular Carbonic Anhydrases biology Hydrogen bond General Chemistry Nuclear magnetic resonance spectroscopy Hydrogen-Ion Concentration Kinetics Solid-state nuclear magnetic resonance chemistry biology.protein Hydroxide Physical chemistry Zinc Isotopes Electric field gradient |
| Zdroj: | Journal of the American Chemical Society. 126(14) |
| ISSN: | 0002-7863 |
| Popis: | The pH dependence of the (67)Zn solid-state nuclear magnetic resonance spectroscopy of human carbonic anhydrase (CAII) has been investigated to characterize the nature of the fourth ligand. CAII, through the Zn(2+)-bound hydroxide, catalyzes the deceptively simple reaction: CO(2) + H(2)O HCO(3)(-) + H(+). The accepted mechanism for CAII would predict that water would be bound to the Zn(2+) at pH 5 and hydroxide would be bound at pH 8.5. The measured values for the electric field gradient (EFG) or quadrupole coupling constant (Cq) for CAII are independent of pH within the limits of the experimental error, i.e., 9.8 +/- 0.2 MHz. The EFG interaction has been predicted by ab initio electronic structure calculations for water and hydroxide bound to the zinc, including various levels of hydrogen bonding. After comparing the predicted Cq's with the experimental values, we conclude that the species present from pH 5-8.5 is the hydroxide form. The NMR data presented here is not consistent with the accepted mechanism for CAII. We show that the NMR data is consistent with an alternative mechanism of CAII. |
| Databáze: | OpenAIRE |
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