Superoxide dismutase inhibitor screening and characterization using ¹?F NMR
- WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
- Megan Elizabeth Arrington (Creator)
- Institution
- Western Carolina University (WCU )
- Web Site: http://library.wcu.edu/
- Advisor
- Jack Summers
Abstract: Superoxide dismutase enzymes (SOD) catalyze the disproportionation of superoxide to
form molecular oxygen and hydrogen peroxide in a cyclic mechanism. SODs prevent
the formation of hydroxyl radicals, preventing apoptosis. Up-regulation of this enzyme
implicates it in the survival of cancer cells and pathogenic bacteria, leading to a call for
SOD inhibitors as potential drugs. 19F NMR based assays were used to study inhibition
of CuZnSOD by flavonol compounds. Flavonols are more effective inhibitors at high pH.
We hypothesize that inhibition at high pH occurs through a two-step reaction, where the
first step is an equilibrium reaction affected by the deprotonation of the inhibitor and the
second step is slower and affected by the deprotonation of the enzyme. The pH
dependence of the second inhibition step is consistent with enzyme deprotonation of
active site Lys 122 at pH=10.1 and is not necessary for the first step. It was also
observed that aggregation of flavonol inhibitors may be occurring and therefore flavonol
binding is stronger than experimentally measured.
To understand the factors that affect binding of flavonols to CuZnSOD, AutoDock
4.0 calculations were carried out and compared to experimental binding constants at pH
8. Experimental binding data show that flavonol diketone tautomerization is not
necessary for binding and that inhibitors bind more effectively above their pKa1 values.
Bis-deprotonated, enol and S-diketone tautomers were predicted to bind CuZnSOD
preferentially in docking results. Computational results indicate that lysine and arginine
residues contribute significantly to binding by hydrogen bonding with flavonol 3,7, and 4'-
oxygens. Despite a strong overall correlation between docking scores for the
deprotonated species and experimental results, apigenin was predicted to have a higher
binding affinity than is experimentally observed. The underlying cause of this
discrepancy is a matter of further investigation.
Superoxide dismutase inhibitor screening and characterization using ¹?F NMR
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Created on 3/1/2010
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Additional Information
- Publication
- Thesis
- Language: English
- Date: 2010
- Subjects
- Superoxide dismutase -- Inhibitors