Document Detail

Resonance Raman studies of xanthine oxidase: The reduced enzyme-product complex with violapterin.
MedLine Citation:
PMID:  16851316     Owner:  NLM     Status:  MEDLINE    
A study of the molecular, electronic, and vibrational characteristics of the molybdenum-containing enzyme complex xanthine oxidase with violapterin has been carried out using density functional theory calculations and resonance Raman spectroscopy. The electronic structure calculations were carried out on a model consisting of the enzyme molybdopterin cofactor [in the four-valent, reduced state; Mo(IV)O(SH)] covalently linked to violapterin (1H,3H,8H-pteridine-2,4,7-trione in the neutral form) via an oxygen bridge, Mo-O-C7. Full geometry optimizations were performed for all models using the SDD basis set and the three-parameter exchange functional of Becke combined with the Lee, Yang, and Parr correlational functional. Harmonic vibrational frequencies were determined for a variety of isotopes in an attempt to correlate experimentally observed shifts upon 18O-labeling of the Mo-OR bridge to bound product as well as shifts seen upon substitution of solvent-exchangeable protons in samples prepared in D2O. The theoretical vibrational frequencies compared favorably with experimentally observed vibrational modes in the resonance Raman spectra of the reduced xanthine oxidase-violapterin complex prepared in H2O and D2O and with 18O-labeled product. Correlating the isotopic shifts from the calculations with those from the resonance Raman experiments resulted in complete normal mode assignments for all modes observed in the 350-1750 cm(-1) range. The present work demonstrates that a model in which the violapterin is coordinated to the molybdenum of the active site in a simple end-on manner via the hydroxyl group introduced by an enzyme accurately predicts the observed resonance Raman spectrum of the complex. Given the numerous modes involving the bridging oxygen, a side-on binding mode can be eliminated.
Craig Hemann; Predrag Ilich; Amy L Stockert; Eun-Young Choi; Russ Hille
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  109     ISSN:  1520-6106     ISO Abbreviation:  J Phys Chem B     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2006-07-20     Completed Date:  2007-06-22     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3023-31     Citation Subset:  IM    
Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
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MeSH Terms
Binding Sites
Coenzymes / chemistry
Deuterium Oxide / chemistry
Metalloproteins / chemistry
Models, Chemical
Models, Molecular
Molecular Conformation
Molybdenum / chemistry
Oxygen / chemistry*
Pteridines / chemistry*
Solvents / chemistry
Spectrophotometry, Ultraviolet
Spectrum Analysis, Raman / methods*
Substrate Specificity
Water / chemistry
Xanthine Oxidase / chemistry*
Grant Support
Reg. No./Substance:
0/Coenzymes; 0/Metalloproteins; 0/Pteridines; 0/Solvents; 2577-38-0/violapterin; 73508-07-3/molybdenum cofactor; 7439-98-7/Molybdenum; 7732-18-5/Water; 7782-44-7/Oxygen; 7789-20-0/Deuterium Oxide; EC Oxidase

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