Issue 39, 2017

Xanthine oxidase–product complexes probe the importance of substrate/product orientation along the reaction coordinate

Abstract

A combination of reaction coordinate computations, resonance Raman spectroscopy, spectroscopic computations, and hydrogen bonding investigations have been used to understand the importance of substrate orientation along the xanthine oxidase reaction coordinate. Specifically, 4-thiolumazine and 2,4-dithiolumazine have been used as reducing substrates for xanthine oxidase to form stable enzyme-product charge transfer complexes suitable for spectroscopic study. Laser excitation into the near-infrared molybdenum-to-product charge transfer band produces rR enhancement patterns in the high frequency in-plane stretching region that directly probe the nature of this MLCT transition and provide insight into the effects of electron redistribution along the reaction coordinate between the transition state and the stable enzyme-product intermediate, including the role of the covalent Mo–O–C linkage in facilitating this process. The results clearly show that specific Mo-substrate orientations allow for enhanced electronic coupling and facilitate strong hydrogen bonding interactions with amino acid residues in the substrate binding pocket.

Graphical abstract: Xanthine oxidase–product complexes probe the importance of substrate/product orientation along the reaction coordinate

Supplementary files

Article information

Article type
Paper
Submitted
11 mei 2017
Accepted
14 jun 2017
First published
11 jul 2017

Dalton Trans., 2017,46, 13242-13250

Xanthine oxidase–product complexes probe the importance of substrate/product orientation along the reaction coordinate

J. Yang, C. Dong and M. L. Kirk, Dalton Trans., 2017, 46, 13242 DOI: 10.1039/C7DT01728F

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