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Second-shell hydrogen bond impacts transition-state structure in bacillus subtilis oxalate decarboxylase

Zhu, Wen, Reinhardt, Laurie A. and Richards, Nigel G. J. 2018. Second-shell hydrogen bond impacts transition-state structure in bacillus subtilis oxalate decarboxylase. Biochemistry 57 (24) , pp. 3425-3432. 10.1021/acs.biochem.8b00214

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Abstract

There is considerable interest in how “second-shell” interactions between protein side chains and metal ligands might modulate Mn(II) ion redox properties and reactivity in metalloenzymes. One such Mn-dependent enzyme is oxalate decarboxylase (OxDC), which catalyzes the disproportionation of oxalate monoanion into formate and CO2. Electron paramagnetic resonance (EPR) studies have shown that a mononuclear Mn(III) ion is formed in OxDC during catalytic turnover and that the removal of a hydrogen bond between one of the metal ligands (Glu101) and a conserved, second-shell tryptophan residue (Trp132) gives rise to altered zero-field splitting parameters for the catalytically important Mn(II) ion. We now report heavy-atom kinetic isotope effect measurements on the W132F OxDC variant, which test the hypothesis that the Glu101/Trp132 hydrogen bond modulates the stability of the Mn(III) ion during catalytic turnover. Our results suggest that removing the Glu101/Trp132 hydrogen bond increases the energy of the oxalate radical intermediate from which decarboxylation takes place. This finding is consistent with a model in which the Glu101/Trp132 hydrogen bond in WT OxDC modulates the redox properties of the Mn(II) ion.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: American Chemical Society
ISSN: 0006-2960
Date of First Compliant Deposit: 24 April 2018
Date of Acceptance: 5 April 2018
Last Modified: 29 Jun 2019 15:45
URI: http://orca.cf.ac.uk/id/eprint/110944

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