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Arylhydrazines as probes of hemoprotein structure and function
1Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco 94143-0446, USA.
Biochimie
|January 1, 1995
Summary
Arylhydrazines react with iron porphyrins to form aryl-iron complexes. Protein-controlled rearrangements yield specific N-arylprotoporphyrin IX isomers, revealing active site details for cytochrome P450 enzymes.
Area of Science:
- Biochemistry
- Organic Chemistry
- Enzymology
Background:
- Arylhydrazines and aryldiazenes react with iron porphyrins and hemoproteins.
- These reactions form sigma-bonded aryl-iron complexes.
Purpose of the Study:
- To investigate the reaction of arylhydrazines with hemoproteins.
- To understand the mechanism of aryl group migration and its implications for active site topology.
- To differentiate between peroxidase and peroxygenase catalysis.
Main Methods:
- Reaction of arylhydrazines with various hemoproteins (hemoglobin, myoglobin, cytochrome P450, etc.).
- Protein denaturation under specific conditions to induce aryl group shift.
- Analysis of N-arylprotoporphyrin IX regioisomer ratios.
Main Results:
- Aryl group shifts to porphyrin nitrogens upon denaturation, forming N-arylprotoporphyrin IX isomers.
- Cytochrome P450 enzymes allow aryl shift without denaturation, providing insights into active site topology.
- Conventional peroxidases yield delta-meso-aryl adducts, not heme adducts, indicating substrate access control.
Conclusions:
- The isomer ratios from intact cytochrome P450 active sites offer direct information on topology and dynamics.
- Restricted substrate access to ferryl oxygen directs reactions towards peroxidase catalysis.