| Autor: |
Rose MJ; Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, California 95064, USA., Betterley NM, Oliver AG, Mascharak PK |
| Jazyk: |
angličtina |
| Zdroj: |
Inorganic chemistry [Inorg Chem] 2010 Feb 15; Vol. 49 (4), pp. 1854-64. |
| DOI: |
10.1021/ic902220a |
| Abstrakt: |
The activity of the non-heme iron enzyme nitrile hydratase (Fe-NHase) is modulated by nitric oxide (NO). The inactive (dark form) NO-bound enzyme is activated when exposed to light via the release of NO from the iron center. In order to determine whether oxygenation of active site Fe-bound Cys-S centers are involved in this process of NO regulation, a model complex (Et(4)N)[(Cl(2)PhPepS)Fe(NO)(DMAP)] (8) has been synthesized and structurally characterized. Complex 8 does not exhibit any NO photolability. However, following oxygenation of the Fe-bound thiolato-S centers to sulfinates (with the aid of oxaziridine), the resulting complex (Et(4)N)[(Cl(2)PhPep{SO(2)}(2))Fe(NO)(DMAP)] (9) releases NO readily upon illumination with visible light. Spectroscopic properties of 8 and 9 confirm that these species do mimic the active site of Fe-NHase closely, and the results indicate that NO photolability is related to S-oxygenation. Results of density functional theory and time-dependent DFT studies on both 8 and 9 indicate that S-oxygenation weakens Fe-S bonding and that strong transitions near 470 nm transfer an electron from a carboxamido-N/sulfinato-SO(2) MO to a dpi(Fe)-pi*(NO)/d(z)2(Fe)-sigma*(NO) antibonding orbital in 9. In case of 8, strong S-Fe-NO bonding interactions prevent the release of NO upon illumination. Together, the results of this work strongly suggest that oxygenated Cys-S centers play an important role in the process of NO regulation of Fe-NHases. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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