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Cofactor processing in galactose oxidase

Lookup NU author(s): Dr Susan Firbank, Dr Margaret Rogers

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Abstract

Galactose oxidase (GO; EC 1.1.3.9) is a monomeric 68 kDa enzyme that contains a single copper and an amino acid-derived cofactor. The mechanism of this radical enzyme has been widely studied by structural, spectroscopic, kinetic and mutational approaches and there is a reasonable understanding of the catalytic mechanism and activation by oxidation to generate the radical cofactor that resides on Tyr-272, one of the copper ligands. Biogenesis of this cofactor involves the post-translational, autocatalytic formation of a thioether cross-link between the active-site residues Cys-228 and Tyr-272. This process is closely linked to a peptide bond cleavage event that releases the N-terminal 17-amino-acid pro-peptide. We have shown using pro-enzyme purified in copper-free conditions that mature oxidized GO can be formed by an autocatalytic process upon addition of copper and oxygen. Structural comparison of pro-GO (GO with the prosequence present) with mature GO reveals overall structural similarity, but with some regions showing significant local differences in main chain position and some active-site-residue side chains differing significantly from their mature enzyme positions. These structural effects of the pro-peptide suggest that it may act as an intramolecular chaperone to provide an open active-site structure conducive to copper binding and chemistry associated with cofactor formation. Various models can be proposed to account for the formation of the thioether bond and oxidation to the radical state; however, the mechanism of prosequence cleavage remains unclear.


Publication metadata

Author(s): Firbank SJ, Rogers M, Hurtado-Guerrero R, Dooley DM, Halcrow MA, Phillips SE, Knowles PF, McPherson MJ

Publication type: Article

Journal: Biochemical Society Transactions

Year: 2003

Volume: 31

Issue: Pt 3

Pages: 506-9

Print publication date: 01/06/2003

ISSN (print): 0300-5127

ISSN (electronic): 1470-8752

Publisher: Portland Press Ltd.

URL: http://dx.doi.org/10.1042/BST0310506

DOI: 10.1042/BST0310506

Notes: GM 27659/GM/United States NIGMS

Journal Article

Research Support, Non-U.S. Gov't

Research Support, U.S. Gov't, P.H.S.

Review

England


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