Showing papers on "Cellobiose dehydrogenase published in 1991"

Cellobiose oxidase from phanerochaete chrysosporium can be cleaved by papain into two domains

Abstract: Cellobiose oxidase from the white rot fungus Phanerochaete chrysosporium has been purified to homogeneity by a new method. The enzyme has been cleaved by papain into two fragments: one containing the heme group and one containing the flavin group. The flavin fragment can oxidize cellobiose and is reoxidized by oxygen. Cellobiose oxidase binds to cellulose to approximately the same extent as cellobiohydrolase I. The cellulose-binding site is located on the flavin domain. The enzyme cannot be totally displaced from cellulose by cellobiose, and it is still active when adsorbed to cellulose. The possible role of the enzyme in lignocellulose degradation is discussed.

Cellobiose dehydrogenases of Sporotrichum (Chrysosporium) thermophile

Abstract: Both cellobiose dehydrogenases of Sporotrichum (Chrysosporium) thermophile, ATCC 42464, obtained after fractionation with DEAE-Trisacryl chromatography and named cellobiose dehydrogenase I and II have been purified to homogeneity by different chromatographic techniques. Both enzymes are slightly glycosylated flavocytochrome-b proteins with similar catalytic properties but with distinct molecular masses (91 kDa and 192 kDa for enzymes I and II, respectively) and isoelectric point (4.1 versus 3.45). Examination by SDS/PAGE clearly showed that the larger enzyme II is a homodimer, whose subunit is close to, but different from dehydrogenase I which is homogeneous by this technique. After limited digestion of both enzymes with papain, two main fractions with residual activity are formed, one carrying the heme, the other being the flavin component; each fraction is characterized by its particular chromatographic behaviour. The flavin carrying component shows an atypical (for flavoprotein) three-banded spectrum indicative of the presence of a flavin derivative. Both enzymes react very slowly with oxygen clearly forming some superoxide radicals and possibly hydrogen peroxide. Cellobiose and other cellodextrins are oxidized at their reducing glycosyl moiety to the corresponding aldonic acid. With the use of the autooxidable phenazinemethosulphate, cellulose (either in a hydrated form or crystalline) is also oxidized at free reducing ends so that appreciable amounts of cellobionic acid are released upon enzymatic hydrolysis.

Effect of β-glucosidase inhibitors on synthesis of cellulase and β-glucosidase in Sporotrichum (Chrysosporium) thermophile

Abstract: The addition of nojirimycin or gluconolactam, substances known as β-glucosidase inhibitors, to cultures of Sporotrichum (Chrysosporium) thermophile growing on cellobiose, caused a twofold or even higher increase (inhibited by cycloheximide) of the intracellular activity of this enzyme, but did not stimulate the synthesis of endocellulase or of cellobiose dehydrogenase. At concentrations from 0.1 to 1.0 mM, nojirimycin stimulated β-glucosidase synthesis to an extent apparently independent of concentration but did not affect cellular respiration on cellobiose. At 5 mM, however, cellobiose assimilation and subsequent growth were significantly but only temporarily impaired and β-glucosidase synthesis, which was still stimulated, was correspondingly delayed. Growth on glucose, on the other hand, was completely unaffected by nojirimycin. Upon fast protein liquid chromatography (FPLC) fractionation by gel filtration of mycelial extracts from cultures grown in the presence and in the absence of nojirimycin (0.1 m...