1uw8

From Proteopedia

Revision as of 16:04, 18 December 2007

CRYSTAL STRUCTURE OF OXALATE DECARBOXYLASE

Overview

Oxalate decarboxylase (EC 4.1.1.2) catalyzes the conversion of oxalate to, formate and carbon dioxide and utilizes dioxygen as a cofactor. By, contrast, the evolutionarily related oxalate oxidase (EC 1.2.3.4) converts, oxalate and dioxygen to carbon dioxide and hydrogen peroxide. Divergent, free radical catalytic mechanisms have been proposed for these enzymes, that involve the requirement of an active site proton donor in the, decarboxylase but not the oxidase reaction. The oxidase possesses only one, domain and manganese binding site per subunit, while the decarboxylase has, two domains and two manganese sites per subunit. A structure of the, decarboxylase together with a limited mutagenesis study has recently been, interpreted as evidence that the C-terminal domain manganese binding site, (site 2) is the catalytic site and that Glu-333 is the crucial proton, donor (Anand, R., Dorrestein, P. C., Kinsland, C., Begley, T. P., and, Ealick, S. E. (2002) Biochemistry 41, 7659-7669). The N-terminal binding, site (site 1) of this structure is solvent-exposed (open) and lacks a, suitable proton donor for the decarboxylase reaction. We report a new, structure of the decarboxylase that shows a loop containing a 3(10) helix, near site 1 in an alternative conformation. This loop adopts a "closed", conformation forming a lid covering the entrance to site 1. This, conformational change brings Glu-162 close to the manganese ion, making it, a new candidate for the crucial proton donor. Site-directed mutagenesis of, equivalent residues in each domain provides evidence that Glu-162 performs, this vital role and that the N-terminal domain is either the sole or the, dominant catalytically active domain.

About this Structure

1UW8 is a Single protein structure of sequence from Bacillus subtilis with MN and TRS as ligands. Active as Oxalate decarboxylase, with EC number 4.1.1.2 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

A closed conformation of Bacillus subtilis oxalate decarboxylase OxdC provides evidence for the true identity of the active site., Just VJ, Stevenson CE, Bowater L, Tanner A, Lawson DM, Bornemann S, J Biol Chem. 2004 May 7;279(19):19867-74. Epub 2004 Feb 10. PMID:14871895

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