Cellulase

Cellulase refers to a class of enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze the cellulolysis (or hydrolysis) of cellulose. However, there are also cellulases produced by other types of organisms such as plants and animals. Several different kinds of cellulases are known, which differ structurally and mechanistically. The EC number for this group of enzymes is [http://expasy.org/enzyme/3.2.1.4 EC 3.2.1.4] .

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

Other names: Endoglucanase. Endo-1,4-beta-glucanase. Carboxymethyl cellulase. Endo-1,4-beta-D-glucanase. Beta-1,4-glucanase. Beta-1,4-endoglucan hydrolase. Celludextrinase. Avicelase.

Types and action

Five general types of cellulases based on the type of reaction catalyzed:
* Endo-cellulase breaks internal bonds to disrupt the crystalline structure of cellulose and expose individual cellulose polysaccharide chains
* Exo-cellulase cleaves 2-4 units from the ends of the exposed chains produced by endocellulase, resulting in the tetrasaccharides or disaccharide such as cellobiose. There are two main types of exo-cellulases (or cellobiohydrolases, abbreviate CBH) - one type working processively from the reducing end, and one type working processively from the non-reducing end of cellulose.
* Cellobiase or beta-glucosidase hydrolyses the exo-cellulase product into individual monosaccharides.
* Oxidative cellulases that depolymerize cellulose by radical reactions, as for instance cellobiose dehydrogenase (acceptor).
* Cellulose phosphorylases that 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 are therefore unable to use most of the energy contained in plant material. Enzymes which 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 non-progressive types. Progressive cellulase will continue to interact with a single polysaccharide strand, non-progressive 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 adaption for working on an insoluble substrate and it allows the enzyme to diffuse two-dimensionally on a surface in a caterpillar way. However, there are also cellulases (mostly endoglucanases) that lacks cellulose binding domain. These enzymes might have a swelling function.

Mechanism of cellulolysis

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

See also

* Hemicellulose


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Look at other dictionaries:

  • cellulase — [ selylaz ] n. f. • 1911; de cellule et ase ♦ Biochim. Enzyme hydrolysant la cellulose. ● cellulase nom féminin Enzyme sécrétée par l intestin ou par les symbiotes intestinaux de certains animaux herbivores et qui permet à ces animaux de digérer… …   Encyclopédie Universelle

  • Cellulase — nach PDB 3L55 …   Deutsch Wikipedia

  • cellulase — [sel′yo͞olās΄] n. [ CELLUL(OSE) + ASE] an enzyme found in some bacteria, fungi, etc. capable of hydrolyzing cellulose into smaller molecules: used in brewing, septic systems, etc …   English World dictionary

  • Cellulase — Une cellulase est une enzyme qui peut décomposer la cellulose. Les cellulases sont classées EC 3.2.1.4. Elles sont produites typiquement par des bactéries, levures et de protozoaires, qui jouent un rôle majeur dans la digestion des animaux, et… …   Wikipédia en Français

  • cellulase — celiuliazė statusas T sritis chemija apibrėžtis Fermentas, hidrolizuojantis celiuliozę. atitikmenys: angl. cellulase rus. целлюлаза …   Chemijos terminų aiškinamasis žodynas

  • cellulase — noun Etymology: International Scientific Vocabulary Date: 1903 an enzyme that hydrolyzes cellulose …   New Collegiate Dictionary

  • cellulase — n. [L. dim. cella, chamber] A digestive enzyme that hydrolyzes cellulose in food …   Dictionary of invertebrate zoology

  • cellulase — /sel yeuh lays , layz /, n. Biochem. any of several enzymes, produced primarily by fungi and bacteria, that catalyze the hydrolysis of cellulose. [1900 05; CELLUL(OSE) + ASE] * * * …   Universalium

  • cellulase — noun An enzyme that catalyze the cellulolysis (or hydrolysis) of cellulose …   Wiktionary

  • cellulase — Endo 1,4 β glucase; an enzyme catalyzing the hydrolysis of 1,4 β glucoside links in cellulose, lichenin, and other β d glucans; found in a variety of microorganisms in soil and in the digestive tracts of herbivores. Used to produce digestive… …   Medical dictionary


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