Enzymatic Hydrolysis of Cellulose: is the Current Theory of the Mechanisms of Hydrolysis Valid?

Enari, Tor-Magnus; Niku‐Paavola, Marja‐Leena

doi:10.3109/07388558709044153

Cited by 141 publications

(41 citation statements)

References 41 publications

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“…The positive result probably reflects a low intrinsic endoglucanase activity (40), which can result in erroneous identification of exocellulases or xylanases as endoglucanases (42). Indeed, it has been suggested previously that there are no strictly exohydrolytic ␤-1,4-glucanases (16,45). Because detection of exohydrolytic activity requires the use of large amounts of enzyme and long incubation times, slight contamination with endoglucanases, especially for enzymes purified from the culture media of cellulolytic organisms, could account for the apparent endoglucanase activities of the enzymes.…”

Section: Discussionmentioning

confidence: 99%

Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities

et al. 1996

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The cenC gene, encoding ␤-1,4-glucanase C (CenC) from Cellulomonas fimi, was overexpressed in Escherichia coli with a tac-based expression vector. The resulting polypeptide, with an apparent molecular mass of 130 kDa, was purified from the cell extracts by affinity chromatography on cellulose followed by anion-exchange chromatography. N-terminal sequence analysis showed the enzyme to be properly processed. Mature CenC was optimally active at pH 5.0 and 45؇C. The enzyme was extremely active on soluble, fluorophoric, and chromophoric glycosides (4-methylumbelliferyl ␤-glycosides, 2-chloro-4-nitrophenyl-␤-D-cellobioside, and 2-chloro-4-nitrophenyl-lactoside) and efficiently hydrolyzed carboxymethyl cellulose, barley ␤-glucan, lichenan, and, to a lesser extent, glucomannan. CenC also hydrolyzed acid-swollen cellulose, Avicel, and bacterial microcrystalline cellulose. However, degradation of the latter was slow compared with its degradation by CenB, another C. fimi cellulase belonging to the same enzyme family. CenC acted with inversion of configuration at the anomeric carbon, in accordance with its classification as a family 9 member. The enzyme released mainly cellobiose from soluble cellodextrins and insoluble cellulose. Attack appeared to be from the reducing chain ends. Analysis of carboxymethyl cellulose hydrolysis suggests that CenC is a semiprocessive enzyme with both endo-and exoglucanase activities.

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Section: Discussionmentioning

confidence: 99%

Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities

et al. 1996

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“…In order to relate metabolism of CBL to its ability to induce cellulase formation, CBH I -the major cellulase of T. reesei (Enari & Niku-Paavola, 1987 however, there was only a low amount of CBH I detectable in culture filtrates from CBL-grown T. reesei. Highest amounts of CBH I were found in cultures grown on cellobiose plus either CBL or 8-gluconolactone.…”

Section: Metabolism O J C B L In T Reesei and Relationship To Cbh Ifmentioning

confidence: 99%

Origin of oxidized cellulose degradation products and mechanism of their promotion of cellobiohydrolase I biosynthesis in Trichoderma reesei

Szakmary

Wotawa

Kubicek

1991

Journal of General Microbiology

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Cellobiono-1,5-lactone (CBL) induces cellulase, particularly cellobiohydrolase I (CBH I) formation in Trichoderma reesei. When used as a sole source of carbon, it promoted comparably poor growth, because (a) the 6-gluconolactone arising by the action of P-glucosidase is not metabolized by the fungus, and (6) it is a low-V,,, substrate of the T. reesei P-glucosidase. Induction of higher amounts of CBH I were observed when CBL was supplied as carbon source together with cellobiose than when supplied alone. Maximal CBH I levels formed under these conditions were comparable to those when T. reesei was grown on cellobiose plus 6-gluconolactone, an inhibitor of P-glucosidase. These data suggest an indirect effect of CBL on CBH I induction, probably by inhibiting cellobiose hydrolysis. The origin of CBL during growth of T. reesei on cellulose was also investigated: aldonic acids and aldonolactones were released from cellulose by T. reesei culture fluids. Artificially oxidized celluloses gave rise to the appearance of higher concentrations of oxidized products but the addition of cellobiose did not, suggesting that their appearance is not due to a cellobiose-oxidizing enzyme. No accumulation of oxidized cellooligosaccharides occurred when the action of both cellobiohydrolases (CBH I and 11) was simultaneously blocked by monoclonal antibodies. These data suggest that cellulose already contains oxidized chain termini, and that these aldonolactones and aldonic acids are released by the action of the two cellobiohydrolases and not by a 'celluloseoxidizing' enzyme.

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“…Typically, endoglucanases (EGs), and cellobiohydrolases (CBH) are the main cellulase enzymes that act synergistically in hydrolyzing a cellulosic substrate [21]. EGs are endo-acting enzymes that function in the hydrolysis of glycosidic bonds, making free ends available for the exo-action of CBH to produce cellobiose and some glucose molecules [22]. However, β-glucosidase is also necessary for reducing the end-product inhibitory effect of cellobiose on CBH via its hydrolytic conversion into glucose [23].…”

Section: Introductionmentioning

confidence: 99%

Molecular Cloning and Expression of Cellulase and Polygalacturonase Genes in E. coli as a Promising Application for Biofuel Production

Ibrahim¹,

Jones²,

Hossenya³

2013

J Pet Environ Biotechnol

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Lignocellulosic biomass has potential for bioethanol, a renewable fuel. A limitation is that bioconversion of the complex lignocellulosic material to simple sugars and then to bioethanol is a challenging process. Recent work has focused on the genetic engineering of a biocatalyst that may play a critical role in biofuel production. Escherichia coli have been considered a convenient host for biocatalysts in biofuel production for its fermentation of glucose into a wide range of short-chain alcohols and production of highly deoxygenated hydrocarbon. The bacterium Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) is notorious for its maceration of the plant cell wall causing soft rot. The ability to destroy plants is due to the expression and secretion of a wide range of hydrolytic enzymes that include cellulases and polygalacturonases. P. carotovorum ATCC™ no. 15359 was used as a source of DNA for the amplification of celB, celC and peh. These genes encode 2 cellulases and a polygalacturonase, respectively. Primers were designed based on published gene sequences and used to amplify the open reading frames from the genomic DNA of P. carotovorum. The individual PCR products were cloned into the pTAC-MAT-2 expression vector and transformed into Escherichia coli. The deduced amino acid sequences of the cloned genes have been analyzed for their catalytically active domains. Estimation of the molecular weights of the expressed proteins was performed using SDS-PAGE analysis and celB, celC and peh products were approximately 29.5 kDa, 40 kDa 41.5 kDa, respectively. Qualitative determination of the cellulase and polygalacturonase activities of the cloned genes was carried out using agar diffusion assays.

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Enzymatic Hydrolysis of Cellulose: is the Current Theory of the Mechanisms of Hydrolysis Valid?

Cited by 141 publications

References 41 publications

Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities

Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities

Origin of oxidized cellulose degradation products and mechanism of their promotion of cellobiohydrolase I biosynthesis in Trichoderma reesei

Molecular Cloning and Expression of Cellulase and Polygalacturonase Genes in E. coli as a Promising Application for Biofuel Production

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