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Cytochrome P450 BM3, NO binding and real-time NO detection
Tobias W B Ost1, Sidong Liu, Simon Daff
1EASTChem School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.
Nitric Oxide : Biology and Chemistry
|February 8, 2011
Summary
Cytochrome P450 BM3 binds nitric oxide (NO) tightly in its ferric state, even with substrates present. This strong binding allows P450 BM3 to be used for accurate NO detection, especially in low-oxygen environments.
Area of Science:
- Biochemistry
- Enzymology
- Bioanalytical Chemistry
Background:
- Nitric oxide (NO) exhibits complex coordination behavior with heme proteins, influencing its reactivity with oxygen.
- Ferric heme complexes with NO are generally more stable in oxygenated environments compared to ferrous complexes.
Purpose of the Study:
- To quantify the binding affinity of nitric oxide (NO) to the ferric state of Cytochrome P450 BM3.
- To investigate the influence of substrate presence on NO binding to ferric Cytochrome P450 BM3.
Main Methods:
- Determination of binding constants (K(d)) for nitric oxide in the ferric state of Cytochrome P450 BM3.
- Comparative analysis of binding affinities in the presence and absence of enzyme substrate.
Main Results:
- Cytochrome P450 BM3 exhibits exceptionally low binding constants for nitric oxide in its ferric state (16 nM with substrate, 40 nM without).
- These low K(d) values suggest a highly hydrophobic active site environment within the enzyme.
- The strong NO binding indicates potential for P450 BM3 as a NO sensor.
Conclusions:
- The high affinity of Cytochrome P450 BM3 for nitric oxide in its ferric state is attributed to its active site's hydrophobicity.
- This characteristic enables the P450 BM3 oxygenase domain for real-time nitric oxide detection assays.
- The enzyme's utility is particularly significant under low-oxygen conditions where conventional methods may fail.
