Structural insight into activity enhancement and inhibition of H64A carbonic anhydrase II by imidazoles
| Autor: | C.M. Maupin, Bhargav Kondeti, Chingkuang Tu, Mayank Aggarwal, David N. Silverman, Robert McKenna |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Stereochemistry
Carbonic anhydrase II human carbonic anhydrase 010402 general chemistry 01 natural sciences Biochemistry imidazole Catalysis 03 medical and health sciences chemistry.chemical_compound Residue (chemistry) Imidazole General Materials Science Binding site lcsh:Science Conformational isomerism 030304 developmental biology 0303 health sciences biology Active site General Chemistry Condensed Matter Physics Lyase Research Papers 3. Good health 0104 chemical sciences chemistry H64A biology.protein rescue activity enhancement activation lcsh:Q |
| Zdroj: | IUCrJ, Vol 1, Iss 2, Pp 129-135 (2014) Iucrj |
| ISSN: | 2052-2525 |
| DOI: | 10.1107/s2052252514004096 |
| Popis: | Human carbonic anhydrases are zinc metalloenzymes that catalyze the hydration and dehydration of CO2 and HCO3 −, respectively. X-ray crystal structures of a variant of human carbonic anhydrase II in complex with four imidazole derivatives (imidazole, 1-methylimidazole, 2-methylimidazole and 4-methylimidazole) have been determined in order to identify the binding sites for such compounds, and a mechanism to explain the effects on catalytic activity is proposed. Human carbonic anhydrases (CAs) are zinc metalloenzymes that catalyze the hydration and dehydration of CO2 and HCO3 −, respectively. The reaction follows a ping-pong mechanism, in which the rate-limiting step is the transfer of a proton from the zinc-bound solvent (OH−/H2O) in/out of the active site via His64, which is widely believed to be the proton-shuttling residue. The decreased catalytic activity (∼20-fold lower with respect to the wild type) of a variant of CA II in which His64 is replaced with Ala (H64A CA II) can be enhanced by exogenous proton donors/acceptors, usually derivatives of imidazoles and pyridines, to almost the wild-type level. X-ray crystal structures of H64A CA II in complex with four imidazole derivatives (imidazole, 1-methylimidazole, 2-methylimidazole and 4-methylimidazole) have been determined and reveal multiple binding sites. Two of these imidazole binding sites have been identified that mimic the positions of the ‘in’ and ‘out’ rotamers of His64 in wild-type CA II, while another directly inhibits catalysis by displacing the zinc-bound solvent. The data presented here not only corroborate the importance of the imidazole side chain of His64 in proton transfer during CA catalysis, but also provide a complete structural understanding of the mechanism by which imidazoles enhance (and inhibit when used at higher concentrations) the activity of H64A CA II. |
| Databáze: | OpenAIRE |
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