Work

Formation of Hexacoordinate Mn(III) in Bacillus subtilis Oxalate Decarboxylase Requires Catalytic Turnover

Year: 2016

Type: article

Abstract: Oxalate decarboxylase (OxDC) catalyzes the disproportionation of oxalic acid monoanion into CO2 and formate. The enzyme has long been hypothesized to utilize dioxygen to form mononuclear Mn(III) or Mn(IV) in the catalytic site during turnover. Recombinant OxDC, however, contains only tightly bound Mn(II), and direct spectroscopic detection of the metal in higher oxidation states under optimal catalytic conditions (pH 4.2) has not yet been reported. Using parallel mode electron paramagnetic resonance spectroscopy, we now show that substantial amounts of Mn(III) are indeed formed in OxDC, but only in the presence of oxalate and dioxygen under acidic conditions. These observations provide the first direct support for proposals in which Mn(III) removes an electron from the substrate to yield a radical intermediate in which the barrier to C-C bond cleavage is significantly decreased. Thus, OxDC joins a small list of enzymes capable of stabilizing and controlling the reactivity of the powerful oxidizing species Mn(III).

Source: Biochemistry

DOI: 10.1021/acs.biochem.5b01340

Authors: Wen Zhu, Jarett Wilcoxen, R. David Britt, Nigel G. J. Richards

Institutions: Indiana University – Purdue University Indianapolis, University of California, Davis

Language: English

Topic: Metal-Catalyzed Oxygenation Mechanisms

Subfield: Inorganic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funders: National Institute of General Medical Sciences, National Institute of Diabetes and Digestive and Kidney Diseases

Awards: G2137469844, Biochemical Studies of Oxalate Decarboxylase, G6056057276, Biochemical Studies of Oxalate Decarboxylase, Mechanisms of Radical SAM Enzymes Probed by EPR Spectroscopy