Glyoxal oxidase

Hammel KE, MD Mozuch, KA Jensen, PJ Kersten (1994) HjOj recycling during oxidation of the arylglycerol P-aryl ether lignin structure by lignin peroxidase and glyoxal oxidase. Biochemistry 33 13349-13354. 

Kersten PJ (1990) Glyoxal oxidase of Phanerochaete chrysosporium its characterization and activation by lignin peroxidase. Proc Natl Acad Sci USA 87 2936-2940. 

Whittaker MM, PJ Kersten, N Nakamura, J Sanders-Loehr, ES Schweizer, JW Whittaker (1996) Glyoxal oxidase from Phanerochaete chrysosporium is a new radical copper oxidase. J Biol Chem 271 681-687. 

The realization of the widespread occurrence of amino acid radicals in enzyme catalysis is recent and has been documented in several reviews (52-61). Among the catalytically essential redox-active amino acids glycyl [e.g., anaerobic class III ribonucleotide reductase (62) and pyruvate formate lyase (63-65)], tryptophanyl [e.g., cytochrome peroxidase (66-68)], cysteinyl [class I and II ribonucleotide reductase (60)], tyrosyl [e.g., class I ribonucleotide reductase (69-71), photosystem II (72, 73), prostaglandin H synthase (74-78)], and modified tyrosyl [e.g., cytochrome c oxidase (79, 80), galactose oxidase (81), glyoxal oxidase (82)] are the most prevalent. The redox potentials of these protein residues are well within the realm of those achievable by biological oxidants. These redox enzymes have emerged as a distinct class of proteins of considerable interest and research activity. 

The active site of GO contains a covalently modified tyrosyl radical coordinated to a Cu(II) ion constituting thereby a novel mononuclear active site in which both the metal ion and a ligand are redox active. Recently, evidence was provided for the same type of active site in glyoxal oxidase (82), which catalyzes the oxidation of aldehydes to carboxylic acids, Eq. (3). 

In 1997, four laboratories reported their results on (phenoxyl)copper(II) structural model compounds that stressed various aspects of the coordination chemistry of GO and glyoxal oxidase in its various oxidation levels. 

Nature has designed the active sites in the enzymes GO and glyoxal oxidase in order to perform a hydrogen-atom abstraction reaction from the a-carbon atom of an O-bound alcoholate (or aldehyde) in the rds. The essence of this chemistry is depicted in Fig. 8. 

Whittaker, M. M., Kersten, P. J., Nakamura, N., Sanders-Loehr, J., Schweizer, E. S., and Whittaker, J. W., 1996b, Glyoxal oxidase from Phanerochaete chrysosporum is a new radical-copper oxidase, J. Biol. Chem. 271 681fi687. 

Glyoxal oxidase from the white-rot wood-metabolizing basidiomycete Phanerochaete chrysosporium has been characterized as a novel radical—copper oxidase. This enzyme exhibits a wide substrate specificity for oxidation of simple aldehydes to the corresponding carboxylic acids according to Equation (5). 

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