Fungal peroxidase: Its structure, function, and application

Arthromyces ramosus, a novel hyphomycete, extracellularly produces a single species of a heme-containing peroxidase. The A. ramosus peroxidase, ARP, shows a broad specificity for hydrogen donors and high catalytic efficiency as does the well-known peroxidase from horseradish roots (HRP). However, it also exhibits unique catalytic properties. These features permit a wide range of applications for ARP, including high-sensitivity chemiluminescent determination of biological materials, protein cross- linking, and dye-transfer inhibition during laundering. The primary and tertiary structures of ARP are very similar to those of the class (II) lignin and manganese peroxidases of the plant peroxidase superfamily. Mechanistic studies of the ARP-catalyzed reaction revealed that it also proceeds with the classical peroxidase cycle; the native ferric ARP undergoes two-electron oxidation by hydrogen peroxide to yield compound (I), followed by two successive one-electron reductions by the hydrogen donor. X-ray crystallography, site-directed mutagenesis, and spectral analyses of ARP have afforded detailed information on the molecular mechanism of the ARP catalysis, and revealed the roles of active site amino acid residues and dynamic features of coordination as well as spin states of heme iron during catalysis.