Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1996 Dec;62(12):4417-27.
doi: 10.1128/aem.62.12.4417-4427.1996.

Purification and Characterization of Cellobiose Dehydrogenases from the White Rot Fungus Trametes versicolor

Purification and Characterization of Cellobiose Dehydrogenases from the White Rot Fungus Trametes versicolor

B P Roy et al. Appl Environ Microbiol. 1996 Dec.

Abstract

The white rot fungus Trametes versicolor degrades lignocellulosic material at least in part by oxidizing the lignin via a number of secreted oxidative and peroxidative enzymes. An extracellular reductive enzyme, cellobiose dehydrogenase (CDH), oxidizes cellobiose and reduces insoluble Mn(IV)O(inf2), commonly found as dark deposits in decaying wood, to form Mn(III), a powerful lignin-oxidizing agent. CDH also reduces ortho-quinones and produces sugar acids which can promote manganese peroxidase and therefore ligninolytic activity. To better understand the role of CDH in lignin degradation, proteins exhibiting cellobiose-dependent quinone-reducing activity were isolated and purified from cultures of T. versicolor. Two distinct proteins were isolated; the proteins had apparent molecular weights of 97,000 and 81,000 and isoelectric points of 4.2 and 6.4, respectively. The larger CDH (CDH 4.2) contained both flavin and heme cofactors, whereas the smaller contained only a flavin (CDH 6.4). These CDH enzymes were rapidly reduced by cellobiose and lactose and somewhat more slowly by cellulose and certain cello-oligosaccharides. Both glycoproteins were able to reduce a very wide range of quinones and organic radical species but differed in their ability to reduce metal ion complexes. Temperature and pH optima for CDH 4.2 were affected by the reduced substrate. Although CDH 4.2 showed rather high substrate specificity among the ortho-quinones, it could also rapidly reduce a structurally very diverse collection of other species, from negatively charged triiodide ions to positively charged hexaquo ferric ions. CDH 6.4 showed a higher K(infm) and a lower V(infmax) and turnover number than did CDH 4.2 for all substrates tested. Furthermore, CDH 6.4 did not reduce the transition metals Fe(III), Cu(II), and Mn(III) at concentrations likely to be physiologically relevant, while CDH 4.2 was able to rapidly reduce even very low concentrations of these ions. The reduction of Fe(III) and Cu(II) by CDH 4.2 may be important in sustaining a Fenton's-type reaction, which produces hydroxyl radicals that can cleave both lignin and cellulose. Unlike the CDH proteins from Phanerochaete chrysosporium, CDH 4.2 and CDH 6.4 are unable to produce hydrogen peroxide.

PubMed Disclaimer

Similar articles

Cited by

References

    1. Methods Enzymol. 1990;186:1-85 - PubMed
    1. Biochem J. 1990 Sep 1;270(2):419-25 - PubMed
    1. Biochem J. 1986 May 15;236(1):221-6 - PubMed
    1. J Biol Chem. 1971 Oct 25;246(20):6339-46 - PubMed
    1. Biochemistry. 1966 Oct;5(10):3181-9 - PubMed

LinkOut - more resources