Cellulase

Cellulases - also written rarely cellulases - are enzymes that are able to break down cellulose into its basic building block of β -glucose.

Natural Occurrence

Plant

Since plants produced even install cellulose in their cell walls, they require endogenous cellulases for the conversion of cell walls, for example, in growth processes. In the plant cellulase is a very old gene.

Prokaryotes

Many prokaryotes bacteria, fungi (wood- degrading organisms) and flagellates possess cellulase genes and therefore are directly capable of cellulose degradation. As endosymbionts they serve many herbivorous animals, which do not have their own cellulase.

Animals without endogenous cellulase

Most animals do not have cellulase and cellulose degradation are dependent upon exogenous cellulases on their endosymbionts. Both ruminants and non-ruminants, the use instead the aid of endosymbiotic prokaryotes in special stomachs or caeca and can only be use the most of the energy in plant foods.

Ruminants digest a large proportion of cellulose and other polysaccharides in the rumen using anaerobic prokaryotes that convert the cellulose into fatty acids. The same is true for horses and water fowl, but in which the processing takes place in the colon.

Man, too, has no digestive enzymes for the degradation of cellulose. With the help of anaerobic bacteria in the first part of the colon, the cecum and the ascending colon is a part of the cellulose is removed from the food to short chain fatty acids. About the colonic mucosa, they are absorbed and utilized by the metabolism. Cellulose is thus adjacent to hemicellulose, pectin and lignin, an important vegetable dietary fiber in the human diet.

Some terrestrial crustaceans as the Isopoda can degrade cellulose with the support endosymbiotischer bacteria. The same is true for insects such as silverfish, almost all termites or cockroaches. In 200 termite species investigated more than 450 different endosymbionts were identified. Endosymbionts fossilized termites have been detected from the Cretaceous directly ( in Burmese amber ).

The fungal cultures of leaf-cutter ants are a Exosymbiose with Egerlingsschirmlingen ( Leucoagaricus gongylophorus ).

Animals with endogenous cellulase

The view that animals generally lack cellulases, however, contradict reports of cellulase evidence. In some animals, the presence of endogenous cellulase or of cellulase could be detected. These include a few representatives of the

• Mollusks, such as some snails: the Snail
• Clams: Corbicula japonica and Lyrodus cellulase genes were detected pedicellatus

• Termite species ( Reticulitermes and Coptotermes formosanus speratus )
• With sterile atmosphere silverfish cellulose degradation was detected, evidence of an endogenous cellulase activity is not unequivocally successful.

Origin and evolution of animal cellulase genes is unheitlich: For nematode horizontal gene transfer, starting from their endosymbionts disclosed. An occurrence of a cellulase gene in the last common ancestor of the Bilateria is assumed, resulting in homologous cellulase genes of this group of animals evolved (vertical gene transfer).

Components

The group of cellulases consists of three different types of enzymes, their interaction rational digestion of cellulose giant molecules ( 3-15 thousand linked glucose molecules) allows:

1 endoglucanases ( EC 3.2.1.4 ) cleave cellulose into large sections ( they can work as a single within the cellulose chains, but only within the so-called amorphous regions where the cellulose molecules are disordered each other and thus build no crystalline regions ). Thus they provide a larger number of chain ends.

Many molecules of the second enzyme, exoglucanases ( EC 3.2.1.91 ) can be a time to this - instead of time- consuming only from one end - work and shorten the cellulose chains continuously by disconnecting always two sugar molecules than double sugar ( disaccharide ) cellobiose.

The molecules of the third enzyme cellobiase or β - glucosidase (EC 3.2.1.21 ) can thus return to work simultaneously and, to finish the decomposition process eventually hydrolyze the β -glycosidic bond between the two glucose molecules of cellobiose and thus the glucose for other metabolic processes ( for example, provide transportation into the blood during digestion ) final.

Use and recovery

Cellulases have several commercial applications in the food, detergent and textile industries. To this end, they are from cultures ( submerged fermentation ) from molds of the genus Trichoderma, particularly T. reesei isolated. These are found in soil and belong to the ascomycetes ( Ascomycota ) on.

In many detergents, cellulases are included. In the textile industry, they are used to give a v. Jean articles on the popular " used" look. In the processing of coffee are used to dissolve the cellulose in the bean during the drying process. Furthermore, cellulases used for the treatment of stomach or intestinal obstruction by undigested plant material ( Phytobezoaren ) and protoplast isolation from plant tissues.