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Ligand and substrate migration in human indoleamine 2,3-dioxygenase
Elena Nickel1, Karin Nienhaus, Changyuan Lu
1Institute of Biophysics, University of Ulm, 89069 Ulm, Germany.
The Journal of Biological Chemistry
|September 22, 2009
Summary
Human indoleamine 2,3-dioxygenase (hIDO) has two L-Trp binding sites. L-Trp can move between sites, affecting enzyme activity and CO binding kinetics, revealing complex substrate interactions.
Area of Science:
- Biochemistry
- Enzymology
- Spectroscopy
Background:
- Human indoleamine 2,3-dioxygenase (hIDO) is a heme enzyme catalyzing L-Trp degradation.
- Understanding hIDO's substrate interaction is crucial for its biological function.
Purpose of the Study:
- Investigate the interplay between ferrous hIDO, CO, and L-Trp.
- Provide evidence for distinct L-Trp binding sites and their functional implications.
Main Methods:
- Fourier transform infrared (FTIR) spectroscopy.
- Optical absorption spectroscopy.
- Kinetic analysis of CO association.
Main Results:
- Identified two distinct L-Trp binding sites on hIDO.
- Observed L-Trp migration from the active site upon CO photodissociation.
- Demonstrated altered CO association kinetics influenced by L-Trp presence in a secondary site.
Conclusions:
- hIDO exhibits complex L-Trp binding dynamics involving at least two sites.
- L-Trp's secondary binding site influences enzyme kinetics even when not directly at the active site.
- These findings elucidate hIDO's regulatory mechanisms and substrate handling.
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