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Reactivity of the Cu-II and tyrosyl free-radical active site of the enzyme macromolecule galactose oxidase (GOase)

Lookup NU author(s): Craig Wright, Emeritus Prof Alfred Sykes


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Studies on the single Cu enzyme galactose oxidase (68kDa; 639 amino acids) from fungal Fusarium NRRL 2903 are considered. The enzyme reacts as a 2e(-) oxidase and catalyses the oxidation of primary alcohols such as D-galactose, RCH2OH + O-2 --> RCHO + H2O2. The Cu-II, similar to 8 Angstrom from the surface, is accessed by a channel, which imposes stereospecific selectivity (e.g. no reaction is observed with L-galactose). The Cu-II is coordinated by Tyr-272, Tyr-495, His-496, His-581 and H2O (the substrate binding site) in a square pyramidal geometry. The active enzyme has a tyrosyl (Tyr) radical at 272, which together with the Cu-II gives the required two-equivalent redox activity. The active form of the enzyme, GOase(ox),, is reformed by the 2e(-) oxidation O-2 --> H2O2. Acid-base properties of the coordinated Tyr-495 and H2O, and binding of NCS-, N-3(-), CH3CO2- and H2PO4- in place of H2O are considered.

Publication metadata

Author(s): Wright C, Sykes AG

Publication type: Article

Publication status: Published

Journal: Macromolecular Symposia

Year: 2000

Volume: 156

Pages: 263-268

ISSN (print): 1022-1360

ISSN (electronic):

Publisher: Wiley - VCH Verlag GmbH & Co


DOI: 10.1002/1521-3900(200007)156:1<263::AID-MASY263>3.0.CO;2-V


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