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Probing cofactor specificity in phenylalanine hydroxylase by molecular dynamics simulations
1Department of Biochemistry and Molecular Biology, University of Bergen, Jonas Liesvei 91, 5009 Bergen, Norway.
Journal of Biomolecular Structure & Dynamics
|May 15, 2003
Summary
The natural cofactor 6R-tetrahydrobiopterin (6R-BH(4)) inhibits phenylalanine hydroxylase (PAH) by binding to Ser23 and blocking L-Phe. Cofactor analogs do not induce this regulatory effect, explaining PAH specificity.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Phenylalanine hydroxylase (PAH) catalyzes L-phenylalanine to L-tyrosine conversion.
- PAH requires tetrahydrobiopterin (BH(4)) as an essential cofactor.
- The natural cofactor 6R-BH(4) uniquely inhibits PAH activity.
Purpose of the Study:
- To investigate the molecular basis for 6R-BH(4) specific inhibition of PAH.
- To understand the conformational changes induced by cofactor binding.
Main Methods:
- Molecular dynamics simulations of PAH alone and complexed with 6R-BH(4), 6S-BH(4), and 6-methyl-tetrahydropterin (6M-PH(4)).
Main Results:
- 6R-BH(4) binding to Ser23 disrupts the enzyme's resting state hydrogen bonding network.
- This interaction facilitates N-terminal binding to the active site iron, blocking L-Phe.
- Cofactor analogs 6S-BH(4) and 6M-PH(4) do not induce this inhibitory conformation.
Conclusions:
- The specific interactions of 6R-BH(4) with Ser23 are crucial for PAH inhibition.
- The N-terminal sequence acts as an intrinsic amino acid regulatory sequence (IARS) upon 6R-BH(4) binding.
- Molecular dynamics simulations elucidate the mechanism of cofactor-specific enzyme regulation.