関: beta-glucosidase

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/02/20 19:28:03」(JST)

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Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases^[1]

Cellulase refers to a suite of enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis (i.e. the hydrolysis of cellulose). However, there are also cellulases produced by a few other types of organisms, such as some termites and the microbial intestinal symbionts of other termites.^[2] Several different kinds of cellulases are known, which differ structurally and mechanistically.

Reaction: Hydrolysis of 1,4-beta-D-glycosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

Other names for 'endoglucanases' are: endo-1,4-beta-glucanase, carboxymethyl cellulase (CMCase), endo-1,4-beta-D-glucanase, beta-1,4-glucanase, beta-1,4-endoglucan hydrolase, and celludextrinase. The other types of cellulases are called exocellulases. The expression 'avicelase' refers almost exclusively to exo-cellulase activity as avicel is a highly micro-crystalline substrate. Cellulase action is considered to be synergistic as all three classes of cellulase can yield much more sugar than the addition of all three separately. Beta-glucosidases can also be considered as yet another group of cellulases.

Types and action

Five general types of cellulases based on the type of reaction catalyzed:

Endocellulase (EC 3.2.1.4) randomly cleaves internal bonds at amorphous sites that create new chain ends.
Exocellulase (EC 3.2.1.91) cleaves two to four units from the ends of the exposed chains produced by endocellulase, resulting in the tetrasaccharides or disaccharides, such as cellobiose. There are two main types of exocellulases [or cellobiohydrolases (CBH)] - CBHI works processively from the reducing end, and CBHII works processively from the nonreducing end of cellulose.
Cellobiase (EC 3.2.1.21) or beta-glucosidase hydrolyses the exocellulase product into individual monosaccharides.
Oxidative cellulases depolymerize cellulose by radical reactions, as for instance cellobiose dehydrogenase (acceptor).
Cellulose phosphorylases depolymerize cellulose using phosphates instead of water.

In the most familiar case of cellulase activity, the enzyme complex breaks down cellulose to beta-glucose. This type of cellulase is produced mainly by symbiotic bacteria in the ruminating chambers of herbivores. Aside from ruminants, most animals (including humans) do not produce cellulase in their bodies and can only partially break down cellulose through fermentation, limiting their ability to use energy in fibrous plant material. Enzymes that hydrolyze hemicellulose are usually referred to as hemicellulase and are usually classified under cellulase in general. Enzymes that cleave lignin are occasionally classified as cellulase, but this is usually considered erroneous.

Within the above types there are also progressive (also known as processive) and nonprogressive types. Progressive cellulase will continue to interact with a single polysaccharide strand, nonprogressive cellulase will interact once then disengage and engage another polysaccharide strand.

Most fungal cellulases have a two-domain structure, with one catalytic domain and one cellulose binding domain, that are connected by a flexible linker. This structure is adapted for working on an insoluble substrate, and it allows the enzyme to diffuse two-dimensionally on a surface in a caterpillar-like fashion. However, there are also cellulases (mostly endoglucanases) that lack cellulose binding domains. These enzymes might have a swelling function.

In many bacteria, cellulases in-vivo are complex enzyme structures organized in supramolecular complexes, the cellulosomes. They contain roughly five different enzymatic subunits representing namely endocellulases, exocellulases, cellobiases, oxidative cellulases and cellulose phosphorylases wherein only endocellulases and cellobiases participate in the actual hydrolysis of the β(1→ 4) linkage. Recent work on the molecular biology of cellulosomes had led to the discovery of numerous cellulosome-related “signature” sequences known as dockerins and cohesins. Depending on their amino acid sequence and tertiary structures, cellulases are divided into clans and families.^[3]

Mechanism of cellulolysis

The three types of reaction catalyzed by cellulases:1. Breakage of the noncovalent interactions present in the amorphous structure of cellulose (endocellulase) 2. Hydrolysis of chain ends to break the polymer into smaller sugars (exocellulase) 3. Hydrolysis of disaccharides and tetrasaccharides into glucose (beta-glucosidase).

Mechanistic details of beta-glucosidase activity of cellulase

Uses

Cellulase is used for commercial food processing in coffee. It performs hydrolysis of cellulose during drying of beans. Furthermore, cellulases are widely used in textile industry and in laundry detergents. They have also been used in the pulp and paper industry for various purposes, and they are even used for pharmaceutical applications. Cellulase is used in the fermentation of biomass into biofuels, although this process is relatively experimental at present. Cellulase is used as a treatment for phytobezoars, a form of cellulose bezoar found in the human stomach.

References

Chapin III, F.S., P.A. Matson, H.A. Mooney. Principles of Terrestrial Ecosystem Ecology. Springer-Verlag New York, NY. 2002
The Merck Manual of Diagnosis and Therapy, Chapter 24
Enhancement of Cellulase Activity from a New Strain of Bacillus subtilis by Medium Optimization and Analysis with Various Cellulosic Substrates, Deepmoni Deka, P. Bhargavi, Ashish Sharma, Dinesh Goyal, M. Jawed, and Arun Goyal. Volume 2011 (2011), Article ID 151656, 8 pages

^ PDB 1NLR; Sulzenbacher G, Shareck F, Morosoli R, Dupont C, and Davies GJ (1997). "The Streptomyces lividans family 12 endoglucanase: construction of the catalytic cre, expression, and X-ray structure at 1.75 Å resolution". Biochemistry 36: 16032–16039. doi:10.1021/bi972407v. PMID 9440876.; rendered with PyMOL
^ A cellulase gene of termite origin. Watanabe H., Hiroaki Noda, Tokuda G., Lo N. 1998 Nature 394, 330-331; Andreas Brune and Moriya Ohkuma, "Role of the termite gut macrobiota in symbiotic digestion", in David Edward Bignell, ed., Biology of Termites: A Modern Synthesis 2010: ch. 16.
^ [1] Bayer E.A, Chanzy H., Lamed R., Shoham Y. (1998): Cellulose, Cellulases and Cellulosomes, Curr Opin Struc Biol 8: 548–557

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1. 胃石 gastric bezoars

English Journal

Microwave-assisted aqueous enzymatic extraction of oil from pumpkin seeds and evaluation of its physicochemical properties, fatty acid compositions and antioxidant activities.

Jiao J, Li ZG, Gai QY, Li XJ, Wei FY, Fu YJ, Ma W.Author information State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040, PR China.AbstractMicrowave-assisted aqueous enzymatic extraction (MAAEE) of pumpkin seed oil was performed in this study. An enzyme cocktail comprised of cellulase, pectinase and proteinase (w/w/w) was found to be the most effective in releasing oils. The highest oil recovery of 64.17% was achieved under optimal conditions of enzyme concentration (1.4%, w/w), temperature (44°C), time (66 min) and irradiation power (419W). Moreover, there were no significant variations in physicochemical properties of MAAEE-extracted oil (MAAEEO) and Soxhlet-extracted oil (SEO), but MAAEEO exhibited better oxidation stability. Additionally, MAAEEO had a higher content of linoleic acid (57.33%) than SEO (53.72%), and it showed stronger antioxidant activities with the IC50 values 123.93 and 152.84, mg/mL, according to DPPH radical scavenging assay and β-carotene/linoleic acid bleaching test. SEM results illustrated the destruction of cell walls and membranes by MAAEE. MAAEE is, therefore, a promising and environmental-friendly technique for oil extraction in the food industry.
Food chemistry.Food Chem.2014 Mar 15;147:17-24. doi: 10.1016/j.foodchem.2013.09.079. Epub 2013 Oct 1.
Microwave-assisted aqueous enzymatic extraction (MAAEE) of pumpkin seed oil was performed in this study. An enzyme cocktail comprised of cellulase, pectinase and proteinase (w/w/w) was found to be the most effective in releasing oils. The highest oil recovery of 64.17% was achieved under optimal con
PMID 24206680

Investigation of lignin deposition on cellulose during hydrothermal pretreatment, its effect on cellulose hydrolysis, and underlying mechanisms.

Li H, Pu Y, Kumar R, Ragauskas AJ, Wyman CE.Author information Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California, 92507; Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, California; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.AbstractIn dilute acid pretreatment of lignocellulosic biomass, lignin has been shown to form droplets that deposit on the cellulose surface and retard enzymatic digestion of cellulose (Donohoe et al., 2008; Selig et al., 2007). However, studies of this nature are limited for hydrothermal pretreatment, with the result that the corresponding mechanisms that inhibit cellulosic enzymes are not well understood. In this study, scanning electron microscope (SEM) and wet chemical analysis of solids formed by hydrothermal pretreatment of a mixture of Avicel cellulose and poplar wood showed that lignin droplets from poplar wood relocated onto the Avicel surface. In addition, nuclear magnetic resonance (NMR) showed higher S/G ratios in deposited lignin than the initial lignin in poplar wood. Furthermore, the lignin droplets deposited on Avicel significantly impeded cellulose hydrolysis. A series of tests confirmed that blockage of the cellulose surface by lignin droplets was the main cause of cellulase inhibition. The results give new insights into the fate of lignin in hydrothermal pretreatment and its effects on enzymatic hydrolysis. Biotechnol. Bioeng. 2014;111: 485-492. © 2013 Wiley Periodicals, Inc.
Biotechnology and bioengineering.Biotechnol Bioeng.2014 Mar;111(3):485-92. doi: 10.1002/bit.25108. Epub 2013 Oct 12.
In dilute acid pretreatment of lignocellulosic biomass, lignin has been shown to form droplets that deposit on the cellulose surface and retard enzymatic digestion of cellulose (Donohoe et al., 2008; Selig et al., 2007). However, studies of this nature are limited for hydrothermal pretreatment, with
PMID 24037461

Cloning and Characterizing the Thermophilic and Detergent Stable Cellulase CelMytB from Saccharophagus sp. Myt-1.

Sakatoku A, Tanaka D, Kamachi H, Nakamura S.Author information Department of Environmental and Energy Science, Faculty of Earth and Environmental Systems, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555 Japan.AbstractWe previously isolated and reported a second species of the Saccharophagus genus, Saccharophagus sp. strain Myt-1. In the present study, a cellulase gene (celMytB) from the genomic DNA of Myt-1 was cloned and characterized. The DNA sequence fragment contained an open reading frame of 1,893 bp that encoded a protein of 631 amino acids with an estimated molecular mass of 66.8 kDa. The deduced protein, CelMytB, had a catalytic domain that contained a conserved signature sequence (VIYEIYNEPL) of glycosyl hydrolase family 5 and a CBM6 cellulose binding module. CelMytB showed optimal activity at 55 °C and pH 6.5, which is similar to the optimal temperature and pH profile of cel5H, an endoglucanase from the closely related S. degradans 2-40. However, the cellulase (degradation of soluble cellulose) and avicelase (degradation of crystalline cellulose) activities of CelMytB were about 3-fold and 100-fold higher, respectively, than the equivalent activities of cel5H. Moreover, CelMytB could degrade xylan. From the zymogram results, we speculated that the catalytic domain of CelMytB had high activity even without the cellulose binding module. The presence of some detergents stimulated the cellulase activity of CelMytB.
Indian journal of microbiology.Indian J Microbiol.2014 Mar;54(1):20-6. doi: 10.1007/s12088-013-0421-0. Epub 2013 Aug 2.
We previously isolated and reported a second species of the Saccharophagus genus, Saccharophagus sp. strain Myt-1. In the present study, a cellulase gene (celMytB) from the genomic DNA of Myt-1 was cloned and characterized. The DNA sequence fragment contained an open reading frame of 1,893 bp that
PMID 24426162

Japanese Journal

Responses of Soil Fungal Populations and Communities to the Thinning of Cryptomeria Japonica Forests

Microbes and Environments 31(1), 19-26, 2016
NAID 130005138791

糸状菌における植物バイオマス分解酵素遺伝子の発現制御

マイコトキシン 66(1), 85-96, 2016
NAID 130005126791

Responses of Soil Fungal Populations and Communities to the Thinning of <i>Cryptomeria Japonica</i> Forests

Microbes and Environments advpub(0), 2016
NAID 130005126465

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リンク元	「beta-glucosidase」

「beta-glucosidase」

Cellulase
	Model of cellulase enzyme, produced by T. fusca, based on PDB structure 1JS4
Identifiers
EC number	3.2.1.4
CAS number	9012-54-8
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
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PMC	articles
PubMed	articles
NCBI	proteins

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関: cellulase

[pmid9440876-1] PDB 1NLR; Sulzenbacher G, Shareck F, Morosoli R, Dupont C, and Davies GJ (1997). "The Streptomyces lividans family 12 endoglucanase: construction of the catalytic cre, expression, and X-ray structure at 1.75 Å resolution". Biochemistry 36: 16032–16039. doi:10.1021/bi972407v. PMID 9440876.; rendered with PyMOL

[2] A cellulase gene of termite origin. Watanabe H., Hiroaki Noda, Tokuda G., Lo N. 1998 Nature 394, 330-331; Andreas Brune and Moriya Ohkuma, "Role of the termite gut macrobiota in symbiotic digestion", in David Edward Bignell, ed., Biology of Termites: A Modern Synthesis 2010: ch. 16.

[3] [1] Bayer E.A, Chanzy H., Lamed R., Shoham Y. (1998): Cellulose, Cellulases and Cellulosomes, Curr Opin Struc Biol 8: 548–557

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cellulase