Evidence that cellobiose oxidase from Phanerochaete chrysosporium is primarily an Fe(III) reductas

Abstract

Kinetic measurements were made for purified cellobiose oxidase in 100 mM acetate (pH 4.0) at 30°C , with excess cellobiose as substrate and O2 or Fe(II1) as acceptor. With 0, at 230 pM as sole electron acceptor, the O2 uptake rate corresponded to a one-electron turnover number of 0.

Escherichia coli flavohaemoglobin (Hmp) reduces cytochrome c and Fe(III)-hydroxamate K by electron transfer from NADH via FAD: sensitivity of oxidoreductase activity to haem-bound dioxygen

“…S ) , as suggested previously for Alcaligenes eutrophus FHP (Probst et al, 1979). Cellobiose oxidase is a fungal enzyme that, like Hmp, contains haem and FAD and, also like Hmp, has an uncertain biological function (Henrikson et al, 1993), although Fe(II1) is proposed to be the physiologically important oxidant (Kremer & Wood, 1992 biose oxidase can use cytochrome c as electron acceptor ; the haem domain facilitates electron transfer to such one-electron acceptors (Henrikson et al, 1993). The 6-type haem ligation (histidine and methionine) of cellobiose oxidase strongly suggests that it has only an electron transfer function (Cox et al, 1992) and does not bind ligands, whereas Hmp binds CO, 0, and other ligands (Ioannidis et al, 1992).…”

A Mechanism for Production of Hydroxyl Radicals by the Brown-Rot Fungus Coniophora Puteana: Fe(III) Reduction by Cellobiose Dehydrogenase and Fe(II) Oxidation at a Distance from the Hyphae

“…3. Above pH 3, almost all Fe(II1) is complexed by three oxalates to form Fe"'(ox) :-, which has a calculated one-electron redox potential of -120 mV, far below the value of + 165 mV measured for CDH from P. chrysosporium at p H 4 (Kremer & Wood, 1992b). This complex is therefore almost certainly not reducible by CDH.…”

“…for 12 d. CDH was assayed as described for Phanerochaete chrysosporium, assuming = 118 mM-l cm-l in cellobiose-minus-untreated &%! !~~~~e spectra, scanned from 440 to 400 nm (Kremer & Wood, 1992b). Its purification was based on Schmidhalter & Canevascini (1993), including DEAE-Sepharose with a gradient of G250 mM NaCl at pH 6.5 (10 mM phosphate buffer), and gel filtration with Sephacryl S-200 (500 ml; pH 6.5).…”

Extracellular Carbohydrate Esterase from the BasidiomyceteCoprinopsis cinereaReleased Ferulic and Acetic Acids from Xylan

“…The publicly available genome database for C. cinerea (http: //www.broadinstitute.org / annotation / genome / coprinus cinereus/MultiHome.html) was searched with the amino acid sequences of known feruloyl esterases, and a gene encoding CcEst1 that had significant identity with these enzymes was found. To clone the gene, C. cinerea strain 5338 7) was grown at 25 C in 200 ml of Kremer and Wood medium, 8) containing 2% w/v Avicel and 0.4% w/v birch wood xylan. The mycelia were harvested after 3 d and subjected to a cloning procedure, as described in a previous report.…”