Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cellobiose”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1977

Fermentation of cellulose and cellobiose by Clostridium thermocellum in the absence of Methanobacterium thermoautotrophicum.

The fermentation of cellulose and cellobiose by Clostridium thermocellum monocultures and C. thermocellum/Methanobacterium thermoautotrophicum cocultures was studied. All cultures were grown under anaerobic conditions in batch culture at 60 degrees C. When grown on cellulose, the coculture exhibited a shorter lag before initiation and growth and celluloysis than did the monoculture. Cellulase activity appeared earlier in the coculture than in the monoculture; however, after growth had ceased, cellulase activity was greater in the monoculture. Monocultures produced primarily ethanol, acetic acid, H2 and CO2. Cocultures produced more H2 and acetic acid and less ethanol than did the monoculture. In the coculture, conversion of H2 to methane was usually complete, and most of the methane produced was derived from CO2 reduction rather than from acetate conversion. Agents of fermentation stoppage were found to be low pH and high concentrations of ethanol in the monoculture and low pH in the coculture. Fermentation of cellobiose was more rapid than that of cellulose. In cellobiose medium, the methanogen caused only slight changes in the fermentation balance of the Clostridium, and free H2 was produced.

Acetates↗
PubMed1996

Cloning of a cDNA encoding cellobiose dehydrogenase, a hemoflavoenzyme from Phanerochaete chrysosporium.

Cellobiose dehydrogenase (CDH) is an extracellular hemoflavoenzyme produced by cellulose-degrading cultures of the wood-degrading basidiomycete Phanerochaete chrysosporium. CDH contains one flavin adenine dinucleotide (FAD) and one heme b per molecule, and it oxidizes cellobiose to cellobionolactone. In this report, a 2.4-kb cDNA encoding CDH was isolated by screening an expression library of P. chrysosporium OGC101 with a CDH-specific polyclonal antibody. The cDNA encodes a 755-amino-acid protein with a predicted mass of 80,115 Da. Sequence analysis suggests that the heme domain is located at the N terminus and that the falvin domain is located at the C terminus. The flavin domain shows a beta 1-alpha A-beta 2 motif for FAD binding and has high sequence similarity to several FAD-dependent enzymes. Little sequence similarity to hemoflavoenzymes is found. CDH binds to cellulose similarly to cellulases. However, little sequence similarity is observed with the conserved cellulose-binding sequences of cellulases. This suggests that CDH might possess a specific sequence for cellulose binding which is different from that of cellulases. Northern (RNA) blot analysis of total RNA from cellulose-, glucose-, and cellobiose-grown P. chrysosporium indicated that CDH mRNA is produced only in cellulose-grown cells. This suggests that CDH expression is regulated at the transcriptional level by either cellulose or one of its degradation products. Southern blot analysis suggests the presence of only a single gene for CDH in P. chrysosporium OGC101.

Amino Acid Sequence↗
PubMed1999

Novel interaction between laccase and cellobiose dehydrogenase during pigment synthesis in the white rot fungus Pycnoporus cinnabarinus.

When glucose is the carbon source, the white rot fungus Pycnoporus cinnabarinus produces a characteristic red pigment, cinnabarinic acid, which is formed by laccase-catalyzed oxidation of the precursor 3-hydroxyanthranilic acid. When P. cinnabarinus was grown on media containing cellobiose or cellulose as the carbon source, the amount of cinnabarinic acid that accumulated was reduced or, in the case of cellulose, no cinnabarinic acid accumulated. Cellobiose-dependent quinone reducing enzymes, the cellobiose dehydrogenases (CDHs), inhibited the redox interaction between laccase and 3-hydroxyanthranilic acid. Two distinct proteins were purified from cellulose-grown cultures of P. cinnabarinus; these proteins were designated CDH I and CDH II. CDH I and CDH II were both monomeric proteins and had apparent molecular weights of about 81,000 and 101,000, respectively, as determined by both gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI values were approximately 5.9 for CDH I and 3.8 for CDH II. Both CDHs used several known CDH substrates as electron acceptors and specifically adsorbed to cellulose. Only CDH II could reduce cytochrome c. The optimum pH values for CDH I and CDH II were 5.5 and 4.5, respectively. In in vitro experiments, both enzymes inhibited laccase-mediated formation of cinnabarinic acid. Oxidation intermediates of 3-hydroxyanthranilic acid served as endogenous electron acceptors for the two CDHs from P. cinnabarinus. These results demonstrated that in the presence of a suitable cellulose-derived electron donor, CDHs can regenerate fungal metabolites oxidized by laccase, and they also supported the hypothesis that CDHs act as links between cellulolytic and ligninolytic pathways.

3-Hydroxyanthranilic Acid↗
PubMed1977

Kinetics of the hydrolysis of cellobiose and p-nitrophenyl-beta-D-glucoside by cellobiase of Trichoderma viride.

Cellobiase has been isolated from the crude cellulase mixture of enzymes of Trichoderma viride using column chromatographic and ion-exchange methods. The steady-state kinetics of the hydrolysis of cellobiose have been investigated as a function of cellobiose and glucose concentrations, pH of the solution, temperature, and dielectric constant, using isopropanol-buffer mixtures. The results show that (i) there is a marked activation of the reaction by initial glucose concentrations of 4 X 10(-3) M to 9 X 10(-2) M and strong inhibition of the reaction at higher initial concentrations, (ii) the log rate -pH curve has a maximum at pH 5.2 and enzyme pK values of 3.5 and 6.8, (iii) the energy of activation at pH 5.1 is 10.2 kcal mol-1 over the temperature range 5-56 degrees C, and (iv) the rate decreases from 0 to 20% (v/v) isopropanol. The hydrolysis by cellobiase (EC 3.2.1.21) of p-nitrophenyl-beta-D-glucoside was examined by pre-steady-state methods in which [enzyme]0 greater than [substrate]0, and by steady-state methods as a function of pH and temperature. The results show (i) a value for k2 of 21 S-1 at pH 7.0 (where k2 is the rate constant for the second step in the assumed two-intermediate mechanism (formula: see text), (ii) a log rate -pH curve, significantly different from that for hydrolysis of cellobiose, in which the rate increases with decreasing pH below pH 4.5, is constant in the region pH 4.5-6, and decreases above pH 6 (exhibiting an enzyme pK value of 7.3), and (iii) an activation energy of 12.5 kcal mol-1 at pH 5.7 over the temperature range 10-60 degrees C.

Cellulase↗
PubMed1994

Creation of metal-complexing agents, reduction of manganese dioxide, and promotion of manganese peroxidase-mediated Mn(III) production by cellobiose:quinone oxidoreductase from Trametes versicolor.

Culture supernatants of the white-rot fungus Trametes versicolor were found to contain Mn(III)-complexing agents able to effectively promote manganese-dependent peroxidase (MnP)-mediated oxidation of phenol red. The high molecular weight fractions of these supernatants contained carbohydrate polymers that functioned as effective Mn(III)-complexing agents. Gluconic and glucuronic acids were also found to be effective Mn(III)-complexing ligands capable of supporting MnP-mediated phenol red oxidation, as was the cellobionic acid formed from cellobiose by cellobiose:quinone oxidoreductase (CBQase) (EC 1.1.5.1). The formation of cellulose-derived sugar acid manganese-complexing agents by CBQase increased in the presence of wood pulp and cellulolytic enzymes. CBQase, while oxidizing cellobiose, reduced insoluble Mn(IV)O2 to Mn(II) or Mn(III) by a reaction whose rate is determined by the nature of the manganese-complexing agents present. A model is proposed to explain how oxidation of carbohydrate and reduction of MnO2 and quinones by CBQase may complement oxidation by MnP, thus promoting lignin biodegradation.

Acids↗
PubMedDate not supplied

Molecular dynamics of polycrystalline cellobiose studied by solid-state NMR.

Molecular motions of polycrystalline cellobiose have been investigated by measuring proton spin-lattice relaxation times, T1 and T1rho, and the second moment, M2, in both protonated and D2O exchanged forms over the temperature range 120-380 K. T1 relaxation is dominated by the motions of hydroxyl groups between 150 and 380 K, characterised by an activation energy of about 8.74 kJ/mol, whereas T1rho relaxation is driven by the motions of the same groups between 120 and 300 K. T1rho results suggest that hydroxyl groups have a distribution of dynamics. Motion of methylene groups was detected in the second-moment experiments at about 350 K, characterised by activation energy of about 40 kJ/mol. Consideration of the calculated and observed rigid-lattice second moments suggests that the reported X-ray data are incorrect for the inter-proton distance on C6'. 13C CPMAS spectra of both protonated and deuterated cellobiose have also been measured. Spectra of the deuterated material showed the existence of a second crystalline form in addition to the normal form.

Cellobiose↗
PubMed2004

The effect of cellobiose, glucose, and cellulose on the survival of Fibrobacter succinogenes A3C cultures grown under ammonia limitation.

The ruminal, cellulolytic bacterium, Fibrobacter succinogenes A3C, grew rapidly on cellulose, cellobiose, or glucose, but it could not withstand long periods of energy source starvation. If ammonia was limiting and either cellobiose or glucose was in excess, the viability declined even faster. The carbohydrate-excess, ammonia-limited cultures did not spill energy, but they accumulated large amounts of cellular polysaccharide. Cultures that were carbohydrate-limited had approximately 4 nmol ATP mg cell protein(-1), but ATP could not be detected in cultures that had an excess of soluble carbohydrates. However, if F. succinogenes A3C was provided with excess cellulose and ammonia was limiting, ATP did not decline, and the cultures digested the cellulose soon after additional nitrogen sources were added. From these results, it appears that excess soluble carbohydrates can promote the death of F. succinogenes, but cellulose does not.

Acids↗
PubMed2005

Enzymatic kinetic of cellulose hydrolysis: inhibition by ethanol and cellobiose.

The ethanol effect on the Trichoderma reesei cellulases was studied to quantify and clarify this inhibition type. To determine inhibition parameters of crude cellulase and purified exoglucanase Cel7A, integrated Michaelis-Menten equations were used assuming the presence of two inhibitors: cellobiose as the reaction product and ethanol as a possible bioproduct of cellulose fermentation. It was found that hydrolysis of cellulose by crude enzyme follows a model that considers noncompetitive inhibition by ethanol, whereas Cel7A is very slightly competitively inhibited. Crude cellulase is much more inhibited (K(iul) = K(icl) = 151.9 mM) than exoglucanase Cel7A (K(icl) = 1.6 x 1015 mM). Also, calculated inhibition constants showed that cellobiose inhibition is more potent than ethanol inhibition both for the crude enzyme as well as exoglucanase Cel7A.

Cellobiose↗
PubMed1992

Uptake of tyramine cellobiose by rat liver.

The uptake of 125I-tyramine cellobiose (TC) by isolated rat hepatocytes and by total rat liver is markedly higher than that of 14C-sucrose and 125I-PVP, suggesting that TC does not enter the cells by fluid phase endocytosis. The distribution of radioactivity after differential centrifugation shows that the compound is shared out amongst sedimentable structures and unsedimentable fraction. Analysis by isopycnic centrifugation indicates that quickly after its penetration into the cells, most of sedimentable 125I-TC is associated with lysosomes. Such an intracellular localization is confirmed by the distributions observed after free flow electrophoresis and by the fact that radioactivity and cathepsin C, a lysosomal hydrolase, are simultaneously released from a mitochondrial fraction treated with glycyl-L-phenylalanine-2-naphthylamide. Pretreatment of the rats with chloroquine, an acidotropic drug that accumulates in lysosomes, prevents to some extent the entry of 125I-TC into these organelles. Experiments performed with purified lysosomes show that 14C-sucrose does not cross the lysosomal membrane when 125I-TC accumulates linearly with time in the fractions. These results are explained by supposing that the linkage of tyramine to cellobiose allow the disaccharide to diffuse through the plasma and the lysosome membranes, and that the accumulation of the molecule in these organelles results from its weak basic properties. 125I-TC could be an interesting molecule with which to study acidotropism in the whole animal and in isolated and cultured cells.

Animals↗
PubMedDate not supplied

Fate of intravenously injected aminated beta(1----3) polyglucose derivatized with 125I-tyraminyl cellobiose.

Aminated beta(1----3)glucan (polyglucose, AG), a potent soluble immunomodulator, was radio-iodinated and traced after intravenous administration to rats. Since the glucose polymer cannot be 125I-labelled directly by conventional methods, the polysaccharide had to be substituted with an adduct which binds the radiolabel. To this end, tyraminyl cellobiose (TC) was coupled to amino groups of AG by means of cyanuric chloride. This procedure resulted in a degree of substitution corresponding to 3.6% (or 1 molecule of tyraminyl cellobiose being incorporated per 28 molecules of glucose). AG substituted with TC (TC-AG) could be labelled with 125I by conventional procedures. After intravenous administration of 125I-TC-AG the serum concentration dropped about 50% from 1 min to about 15 min after injection, while a further drop from 50% to about 25% was observed during the next 15-60 min. The finding that 60 min after injection most of the radioactivity was recovered in the kidneys and urine, together with the results from gel chromatography showing that the low Mw fraction of the injected material disappeared first from the circulation, suggests that the initial rapid phase of elimination is due mainly to glomerular filtration. The molecules that are too large for kidney excretion are taken up mainly by the liver (about 10% of injected dose) at a slower speed. This notion was supported by the finding that a preparation of high Mw glucan obtained by gel chromatography survived for a long period in the circulation, and was eliminated mainly by accumulation in liver, whereas a preparation of low Mw glucan was rapidly eliminated by glomerular filtration. Several days after injection the liver contained nearly 90% of the recovered radioactivity, whereas the kidneys and other organs contained only insignificant amounts. This indicates that radioactivity associated with the kidneys after 60 min reflects glomerular filtration, whereas radioactivity in liver results from uptake leading to lysosomal accumulation. Isolation of liver cells after injection disclosed that the radioactivity per cell was the same in Kupffer cells (KC) and liver endothelial cells (LEC), whereas the uptake per parenchymal cell (PC) was about 30% of the uptake per KC and LEC. It could be calculated that in the intact liver, the population of PC was responsible for 50% of the uptake, whereas the populations of LEC and KC contained 35% and 15%, respectively, of the total liver radioactivity. These findings raise the question whether not only KC, but also LEC and PC may be mediators of the immune responses caused by beta(1----3) polyglucose.

Adjuvants, Immunologic↗
PubMedDate not supplied

The cellobiose permease of Escherichia coli consists of three proteins and is homologous to the lactose permease of Staphylococcus aureus.

The cellobiose (cel) operon of Escherichia coli was recently sequenced and shown to consist of five genes, celABCDF (Parker and Hall, 1990). We have shown that the CelA, CelB and CelC proteins possess amino acid sequences which are homologous to different domains of the lactose permease of Staphylococcus aureus. CelB corresponds to the integral membrane portion of the permease (IIcel) while CelC (IIIcel) and CelA (IVcel) correspond to the two cytoplasmic domains which appear to comprise the first and second phosphorylation sites in the permease, respectively. The cellobiose permease is the only one of several homologous sequenced permeases of the phosphoenolpyruvate:sugar phosphotransferase system which has its three known functional domains residing on distinct polypeptide chains.

Amino Acid Sequence↗
PubMed2005

Electrochemical investigation of cellobiose dehydrogenase from new fungal sources on Au electrodes.

Following previous electrochemical investigations of cellobiose dehydrogenase (CDH), the present investigation reports on the initial screening of the electrochemistry of three new CDHs, two from the white rot basidiomycetes Trametes villosa and Phanerochaete sordida and one from the soft rot ascomycete Myriococcum thermophilum, for their ability to directly exchange electrons with 10 different alkanethiol-modified Au electrodes. Direct electron transfer (DET) between the enzymes and some of the modified Au electrodes was shown, both, in the presence and in the absence of cellobiose. However, the length and the head functionality of the alkanethiols drastically influenced the efficiency of the DET reaction and also influenced the effect of pH on the biocatalytic/redox currents, suggesting the importance of structural/sequence differences between these CDH enzymes. In this respect, the white rot CDHs exhibit excellent biocatalytic and redox currents, whereas for the soft rot CDH the DET communication is much less efficient. Cyclic voltammograms indicate that the heme domain of the CDHs is the part of the enzymes that most readily exchanges electrons with the electrode. However, for P. sordida CDH on 11-mercaptoundecanol or dithiopropionic acid-modified Au electrodes, a second voltammetric wave was noticed suggesting that for some orientations of the enzyme, DET communication with the FAD cofactor can also be obtained.

Biosensing Techniques↗
PubMed2005

Ethanol production from cellobiose by Zymobacter palmae carrying the Ruminocuccus albus beta-glucosidase gene.

Its metabolic characteristics suggest Zymobacter palmae gen. nov., sp. nov. could serve as a useful new ethanol-fermenting bacterium, but its biotechnological exploitation would require certain genetic improvements. We therefore established a method for transforming Z. palmae using the broad-host vector plasmids pRK290, pMFY31 and pMFY40 as a source of transforming DNA. Using electroporation, the frequency of transformation was 10(5) to 10(6) transformants/mug of DNA. To confer the ability to ferment cellobiose, which is a hydrolysis product from cellulosic materials treated enzymatically or with acid, the beta-glucosidase gene from Ruminococcus albus was introduced into Z. palmae, where its expression was driven by its endogenous promoter. About 56% of the enzyme expressed was localized on the cell-surface or in the periplasm. The recombinant Z. palmae could ferment 2% cellobiose to ethanol, producing 95% of the theoretical yield with no accumulation of organic acids as metabolic by-products. Thus, expression of beta-glucosidase in Z. palmae expanded the substrate spectrum of the strain, enabling ethanol production from cellulosic materials.

Cellobiose↗
PubMed1999

Transglycosylation of cellobiose by partially purified Trichoderma viride cellulase.

A commercial cellulase from Trichoderma viride was fractionated into three fractions, F1, F2, and F3, in order to investigate transglycosylation activities. Among these fractions, F3, which demonstrated highly hydrolytic activity toward p-nitrophenyl beta-D-glucopyranoside and Avicel, most effectively catalyzed the transglycosylation of cellobiose and converted cellobiose into beta-Glc-(1-->6)-beta-glc-(1-->4)-Glc and beta-Glc-(1-->6)-beta-Glc-(1-->6)-beta-Glc(1-->4)-Glc. The F3 fraction contained the enzyme to catalyze beta-glucosyl transfer toward only the C-6 position of the sugar acceptor, and thus it is expected to be of use for syntheses of functional oligosaccharides.

Carbohydrate Sequence↗
PubMed2002

Oxygen reduction by cellobiose oxidoreductase: the role of the haem group.

We have used optical and electron paramagnetic spectroscopy to study the flavohaem enzyme cellobiose oxidoreductase (CBOR) from Phanerochaete chrysosporium. We have examined redox cycles of the enzyme in which the oxidation of cellobiose to cellobionolactone is coupled to the reduction of oxygen. During turnover flavin can reduce oxygen with one electron to produce superoxide or two electrons to produce hydrogen peroxide. Addition of superoxide dismutase significantly extended the time courses of these cycles, slowing the re-oxidation rate of both cofactors. Addition of catalase also affected the haem time course, but to a lesser extent. Experiments in which superoxide was generated in the reaction mixture showed that this radical greatly enhanced the rate of haem re-oxidation. From these results we propose a mechanism in which reactive oxygen species generation by CBOR flavin subsequently re-oxidises CBOR haem. We discuss this mechanism in relationship to the biological function of this enzyme, namely lignocellulose degradation.

Carbohydrate Dehydrogenases↗
PubMed1999

Induction of lactate production associated with a decrease in NADH cell content enables growth resumption of Clostridium cellulolyticum in batch cultures on cellobiose.

When grown in batch cultures in fermentors with 23.4 mM cellobiose, Clostridium cellulolyticum displayed biphasic growth kinetics not associated with sequential substrate consumption and which led to a twofold higher production of biomass than previously reported. In the first growth phase, acetate was the major product of cellobiose metabolism, since lactate and ethanol productions remained low. Furthermore, an accumulation of intracellular NADH was observed. The transition towards the second growth phase was accompanied by an induction of lactate production, in such a way that lactate became the major product of C. cellulolyticum metabolism. In addition, a decrease in NADH concentration was measured, concomitant with this induction of lactate production and with the growth resumption. During both growth phases, the NADH-ferredoxin reductase-hydrogenase system played a major function in NADH regeneration, since H2 production was 1.4- to 1.5-fold higher than that of CO2. Thus, we found that lactate production serves as an additional catabolic pathway enabling C. cellulolyticum to cope with excesses of carbon and NADH produced. Growth experiments on C. cellulolyticum under an atmosphere of carbon monoxide mimicked this phenomenon and confirmed that a high intracellular level of NADH can provide a barrier to bacterial growth.

Acetates↗
PubMed1988

Synthesis and radioiodination of tyramine cellobiose for labeling monoclonal antibodies.

A tyramine cellobiose (TCB) adduct was synthesized by the reductive amination of cellobiose by tyramine with a product yield of 78%. The TCB adduct was purified by chromatography and then iodinated using the chloramine-T method. After iodination, the adduct was activated with cyanuric chloride and linked to protein by incubation at room temperature for 2 h. Immunoreactivity and avidity were well maintained compared to electrophilically radioiodinated 1A14 whole antibody. The tumor uptake and retention were strikingly greater with iodinated TCB-antibody compared to that of the conventionally iodinated antibody; whereas, the plasma clearance curve and uptake in other organs were not changed. This method of labeling increases the retention time of radioiodine in tumors and thus extends to iodinated antibodies one of the advantages of indium labels, namely that the isotope is not readily washed out of the tumor after it becomes localized.

Animals↗
PubMed1998

Structure of the Bacillus agaradherans family 5 endoglucanase at 1.6 A and its cellobiose complex at 2.0 A resolution.

The enzymatic degradation of cellulose, by cellulases, is not only industrially important in the food, paper, and textile industries but also a potentially useful method for the environmentally friendly recycling of municipal waste. An understanding of the structural and mechanistic requirements for the hydrolysis of the beta-1,4 glycosidic bonds of cellulose is an essential prerequisite for beneficial engineering of cellulases for these processes. Cellulases have been classified into 13 of the 62 glycoside hydrolase families [Henrissat, B., and Bairoch, A. (1996) Biochem J. 316, 695-696]. The structure of the catalytic core of the family 5 endoglucanase, Ce15A, from the alkalophilic Bacillus agaradherans has been solved by multiple isomorphous replacement at 1.6 A resolution. Ce15A has the (alpha/beta)8 barrel structure and signature structural features typical of the grouping of glycoside hydrolase families known as clan GH-A, with the catalytic acid/base Glu 139 and nucleophile Glu 228 on barrel strands beta 4 and beta 7 as expected. In addition to the native enzyme, the 2.0 A resolution structure of the cellobiose-bound form of the enzyme has also been determined. Cellobiose binds preferentially in the -2 and -3 subsites of the enzyme. Kinetic studies on the isolated catalytic core domain of Ce15A, using a series of reduced cellodextrins as substrates, suggest approximately five to six binding sites, consistent with the shape and size of the cleft observed by crystallography.

Bacillus↗