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Spectroscopic and electronic structure studies of 2,3-dihydroxybiphenyl 1,2-dioxygenase: O2 reactivity of the non-heme ferrous site in extradiol dioxygenases.

Authors :
Davis MI
Wasinger EC
Decker A
Pau MY
Vaillancourt FH
Bolin JT
Eltis LD
Hedman B
Hodgson KO
Solomon EI
Source :
Journal of the American Chemical Society [J Am Chem Soc] 2003 Sep 17; Vol. 125 (37), pp. 11214-27.
Publication Year :
2003

Abstract

The extradiol dioxygenase, 2,3-dihydroxybiphenyl 1,2-dioxygenase (DHBD, EC 1.13.11.39), has been studied using magnetic circular dichroism (MCD), variable-temperature variable-field (VTVH) MCD, X-ray absorption (XAS) pre-edge, and extended X-ray absorption fine structure (EXAFS) spectroscopies, which are analogous to methods used in earlier studies on the extradiol dioxygenase catechol 2,3-dioxygenase [Mabrouk et al. J. Am. Chem Soc. 1991, 113, 4053-4061]. For DHBD, the spectroscopic data can be correlated to the results of crystallography and with the results from density functional calculations to obtain detailed geometric and electronic structure descriptions of the resting and substrate (DHB) bound forms of the enzyme. The geometry of the active site of the resting enzyme, square pyramidal with a strong Fe-glutamate bond in the equatorial plane, localizes the redox active orbital in an orientation appropriate for O(2) binding. However, the O(2) reaction is not favorable, as it would produce a ferric superoxide intermediate with a weak Fe-O bond. Substrate binding leads to a new square pyramidal structure with the strong Fe-glutamate bond in the axial direction as indicated by a decrease in the (5)E(g) and increase in the (5)T(2g) splitting. Electronic structure calculations provide insight into the relative lack of dioxygen reactivity for the resting enzyme and its activation upon substrate binding.

Details

Language :
English
ISSN :
0002-7863
Volume :
125
Issue :
37
Database :
MEDLINE
Journal :
Journal of the American Chemical Society
Publication Type :
Academic Journal
Accession number :
16220940
Full Text :
https://doi.org/10.1021/ja029746i