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投稿者: Yuma Morimoto

Pyranopterin Dithiolene Distortions Relevant to Electron Transfer in Xanthine Oxidase/Dehydrogenase

† Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001,United States
‡ Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Karl-Liebknecht Strasse 24−25, 14476 Potsdam, Germany
Inorg. Chem., Article ASAP
DOI: 10.1021/ic500873y
Publication Date (Web): June 30, 2014
Copyright © 2014 American Chemical Society
*E-mail: sleim@uni-potsdam.de., *E-mail: mkirk@unm.edu.

Synopsis

The reducing substrates 4-thiolumazine and 2,4-dithiolumazine have been used to form MoIV-product complexes in xanthine oxidase (XO) and xanthine dehydrogenase (XDH). The MoIV-product complexes absorb in the near-infrared (NIR) region of the spectrum. Optical pumping into this NIR metal-to-ligand charge-transfer band reveals in-plane bending modes of the bound product in addition to low-frequency molybdenum dithiolene and pyranopterin dithiolene (pyranopterin ditholene) vibrational modes. The work provides insight into how pyranopterin ditholene is coupled to redox changes at the Mo site and how pyranopterin ditholene functions as an electron-transfer conduit in the oxidative half-reaction of XO/XDH.

Abstract

Abstract Image
The reducing substrates 4-thiolumazine and 2,4-dithiolumazine have been used to form MoIV-product complexes with xanthine oxidase (XO) and xanthine dehydrogenase. These MoIV-product complexes display an intense metal-to-ligand charge-transfer (MLCT) band in the near-infrared region of the spectrum. Optical pumping into this MLCT band yields resonance Raman spectra of the Mo site that are devoid of contributions from the highly absorbing FAD and 2Fe2S clusters in the protein. The resonance Raman spectra reveal in-plane bending modes of the bound product and low-frequency molybdenum dithiolene and pyranopterin dithiolene vibrational modes. This work provides keen insight into the role of the pyranopterin dithiolene in electron-transfer reactivity.
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