Cellulases

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Cellulases
Cellulases
according to PDB  3L55
Enzyme Classifications
EC, category 3.2.1.4 ,  hydrolase
Response type Endohydrolysis of 1,4-β-D-glucosidic bonds
Substrate Cellulose, Lichenin, & β-D-Glucans
EC, category 3.2.1.91 ,  hydrolase
Response type Hydrolysis of the 1,4-β-D-glucosidic bonds of the cellulose starting from the non-reducing end of the cellulose chain
Substrate Cellulose
Products Cellobiose
EC, category 3.2.1.21 ,  hydrolase
Response type Hydrolysis of 1,4-β-D-glucosidic bonds
Substrate Cellobiose
Products beta-D-glucose
Occurrence
Parent taxon Bacteria, fungi

Cellulases - rarely cellulases written - are enzymes which are capable of the β-1,4- glucoside bond of cellulose cleaving, whereby glucose is released.

Natural occurrence

plants

Since plants build cellulose they produce themselves into their cell walls, they need endogenous cellulases to remodel cell walls, e.g. B. in growth processes . The plant cellulase gene is a very old gene.

Prokaryotes

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

Animals without endogenous cellulase

Most animals have no cellulase genes and are dependent on exogenous cellulases from their endosymbionts to break down cellulose . Instead, both ruminants and non-ruminants use the help of endosymbiotic prokaryotes in special stomachs or appendixes, and this is the only way they can use the majority of the energy in plant-based food.

Ruminants digest a large part of the cellulose and other polysaccharides in the rumen with the help of anaerobic prokaryotes, which convert the cellulose into fatty acids. The same applies to horses and water fowl , where processing takes place in the large intestine .

Humans also have no digestive enzymes to break down cellulose. With the help of anaerobic bacteria in the first part of the large intestine, the appendix and the ascending colon , some of the cellulose from food is broken down into short-chain fatty acids . They are absorbed through the colon mucosa and used by the metabolism . In addition to hemicelluloses , pectin and lignin , cellulose is an important vegetable fiber in human nutrition.

Some terrestrial crustaceans, such as the Isopoda, can break down cellulose with the help of endosymbiotic bacteria. The same goes for insects like silverfish , almost all termites or cockroaches . More than 450 different endosymbionts were identified in 200 termite species examined. Endosymbionts of fossil termites have already been detected directly (in Burmese amber) from the Cretaceous period.

The fungal cultures of the leaf cutter ants are an exosymbiosis with Egerling umbrellas ( Leucoagaricus gongylophorus ).

Endogenous cellulase animals

However, reports of cellulase detection contradict the view that animals generally lack cellulases. The presence of endogenous cellulase or cellulase genes has been demonstrated in some animals. These include a few representatives of the

The origin and evolution of the animal cellulase genes are inconsistent: a horizontal gene transfer based on their endosymbionts has been announced for nematodes . It is assumed that a cellulase gene occurs in the last common ancestor of the Bilateria , from which homologous cellulase genes of this group of animals evolved ( vertical gene transfer ).

Components

The three main enzymes involved in the breakdown of cellulose catalyze three reactions: 1) separation of non-covalent bonds between fibers (endocellulase); 2) hydrolysis of individual fibers (exocellulase); 3) hydrolysis of tetra- and disaccharides (β-glucosidase)

The group of cellulases consists of three different types of enzymes, the interaction of which enables an efficient digestion of the giant cellulose molecules (3 - 15 thousand linked glucose molecules):

1. Endoglucanases ( EC  3.2.1.4 ) split cellulose into larger sections (they are the only ones able to work within the cellulose chains, but only within so-called amorphous areas, where the cellulose molecules are disordered and therefore do not build up any crystalline areas). As a result, they create a larger number of chain ends.

Many molecules of the second enzyme, the exoglucanases ( EC  3.2.1.91 ) can then work on these at the same time - instead of time-consuming only from one end - and continuously shorten the cellulose chains by always separating two sugar molecules as double sugar ( disaccharide ) cellobiose .

The molecules of the 3rd enzyme cellobiase or β-glucosidase ( EC  3.2.1.21 ) can work simultaneously again and, at the end of the decomposition process, finally hydrolyze the β-glycosidic connection between the two glucose molecules of cellobiose and thus the glucose for further metabolic processes ( e.g. transport into the blood during digestion).

Use and extraction

Cellulases have several commercial uses in the food, detergent, and textile industries. For this purpose, they are isolated from cultures ( submerged fermentation ) of molds of the genus Trichoderma , in particular T. reesei . These are found in the soil and belong to the hose mushrooms (Ascomycota) to.

Cellulases are found in many detergents . In the textile industry, they are used to v. a. To give jeans items the popular "used look". In coffee processing they are used to dissolve the cellulose in the beans during the drying process. Furthermore, cellulases are used for the treatment of gastric or intestinal obstruction caused by undigested plant material ( phytobezoars ) and for protoplast isolation from plant tissues.

Individual evidence

  1. ↑ Angus Davison, Mark Blaxter: Ancient origin of glycosyl hydrolase family 9 cellulase genes. In: Molecular Biology and Evolution. Volume 22, No. 5, 2005, pp. 1273-1284.
  2. ^ William Trager: The cultivation of a cellulose-digesting flagellate, Trichomonas termopsidis, and of certain other termite protozoa. In: The Biological Bulletin. Volume 66, No. 2, 1934, pp. 182-190.
  3. ↑ Michael A. Yamin: Cellulose metabolism by the flagellate Trichonympha from a termite is independent of endosymbiotic bacteria. In: Science. Volume 211, No. 4477, 1981, pp. 58-59.
  4. ↑ M. Zimmer et al .: Cellulose digestion and phenol oxidation in coastal isopods (Crustacea: Isopoda). In: Marine Biology. Volume 140, No. 6, 2002, pp. 1207-1213, doi: 10.1007 / s00227-002-0800-2 .
  5. ↑ Martin Zimmer, Werner Topp: Microorganisms and cellulose digestion in the gut of the woodlouse Porcellio scaber. In: Journal of Chemical Ecology. Volume 24, No. 8, 1998, pp. 1397-1408, doi: 10.1023 / A: 1021235001949 .
  6. ↑ N. Chakraborty, GM Sarkar, SC Lahiri: Cellulose degrading capabilities of cellulolytic bacteria isolated from the intestinal fluids of the silver cricket. In: Environmentalist. Volume 20, No. 1, 2000, pp. 9-11.
  7. ↑ Moriya Ohkuma: Symbioses of flagellates and prokaryotes in the gut of lower termites. In: Trends in Microbiology. Volume 16, No. 7 2008, pp. 345-362. doi: 10.1016 / j.tim.2008.04.004
  8. ^ Andreas Brune, Ulrich Stingl: Procaryotic symbionts of termite gut flagellates: Phylogenetic and metabolic implications of a tripartite symbiosis. In: Jörg Overmann (Ed.): Progress in Molecular and Subcellular Biology. Volume 41, Springer Verlag, 2005, ISBN 3-540-28210-6 .
  9. ↑ Michael Slaytor: Cellulose digestion in termites and cockroaches: what role do symbionts play? . In: Comparative Biochemistry and Physiology. Part B: Comparative Biochemistry. Volume 103, No. 4, 1992, pp. 775-784, doi: 10.1016 / 0305-0491 (92) 90194-V .
  10. ↑ Michael A. Yamin: Flagellates of the orders Trichomonadida Kirby, Oxymonadida Grasse, and Hypermastigida Grassi & Foa reported from lower termites (Isoptera families Mastotermitidae, Kalotermitidae, Hodotermitidae, Termopsidae, Rhinotermitidae, and Serritermitidae feeding roachryptermitidae) and from the wood Dictyoptera: Cryptocercidae). In: Sociobiology. Volume 4, 1979, pp. 113-117.
  11. ↑ George O Poinar Jr: Description of an early cretaceous termite (Isoptera: Kalotermitidae) and its associated intestinal protozoa, with comments on their co-evolution. In: Parasites & Vectors. Volume 2, 2009, p. 12, doi: 10.1186 / 1756-3305-2-12 open access
  12. ↑ a b entry on cellulose. In: Römpp Online . Georg Thieme Verlag, accessed on August 9, 2013.
  13. ↑ Fay L. Myers, DH Northcote: Partial Purification and some Properties of a Cellulase from Helix pomatia. (PDF; 1.3 MB). Department of Biochemistry, University of Cambridge, July 23, 1958.
  14. ↑ EC 3.2.1.4 - cellulase . at: BRENDA . Retrieved August 9, 2013.
  15. ↑ Benjamin J. Allardyce, Stuart M. Linton: and characterization of endo-β-1, 4-glucanase and laminarinase enzymes from the gecarcinid land crab Gecarcoidea natalis and the aquatic crayfish Cherax destructor. In: Journal of Experimental Biology. Volume 211, No. 14, 2008, pp. 2275-2287.
  16. ^ Allison C. Crawford, Neil R. Richardson, Peter B. Mather: A comparative study of cellulase and xylanase activity in freshwater crayfish and marine prawns. In: Aquaculture Research. Volume 36, No. 6, 2005, pp. 586-592.
  17. ↑ Beetle parasite with unusual genes: Genome of the nematode Pristionchus pacificus decoded. go.de, September 22, 2008, accessed July 1, 2012 .
  18. ^ H. Watanabe, Hiroaki Noda, G. Tokuda N. Lo: A cellulase gene of termite origin. In: Nature . 394, 1998, pp. 330-331.
  19. ↑ Andreas Brune, Moriya Ohkuma: Role of the termite gut macrobiota in symbiotic digestion. In: David Edward Bignell (Ed.): Biology of Termites: A Modern Synthesis. 2010, chapter 16.
  20. ↑ K. Nakashima et al .: Dual cellulose-digesting system of the wood-feeding termite, Coptotermes formosanus Shiraki. In: Insect Biochemistry and Molecular Biology. Volume 32, No. 7, 2002, pp. 777-784.
  21. ↑ Michael M. Martin, Joan S. Martin: Cellulose digestion in the midgut of the fungus-growing termite Macrotermes natalensis: The role of acquired digestive enzymes. In: Science. Volume 199, No. 4336, 1978, pp. 1453-1455.
  22. ↑ Hirofumi Watanabe et al: A cellulase gene of termite origin. In: Nature. Volume 394, No. 6691, 1998, pp. 330-331.
  23. ↑ Gerhard Heldmaier, Gerhard Neuweiler: Vegetative Physiology . In: Comparative Animal Physiology . tape 2 . Springer, 2004, ISBN 3-540-00067-4 , pp. 327 ( limited preview in Google Book search).
  24. ↑ John T. Jones, Cleber Furlanetto, Taisei Kikuchi: Horizontal gene transfer from bacteria and fungi as a driving force in the evolution of plant parasitism in nematodes. ( Memento of the original from September 21, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Nematology. Volume 7, No. 5, 2005, pp. 641-646. @1@ 2Template: Webachiv / IABot / www.ingentaconnect.com
  25. ↑ Werner E. Mayer et al .: Horizontal gene transfer of microbial cellulases into nematode genomes is associated with functional assimilation and gene turnover. In: BMC Evolutionary Biology. Volume 11, No. 1, 2011, p. 13.
  26. ↑ Nathan Lo, Hirofumi Watanabe, Masahiro Sugimura: Evidence for the presence of a cellulase gene in the last common ancestor of bilaterian animals. In: Proceedings of the Royal Society of London. Series B: Biological Sciences. 270, Suppl 1 2003, p. S69-S72.

literature

  • FS Chapin, PA Matson, HA Mooney: Principles of Terrestrial Ecosystem Ecology. Springer-Verlag, New York 2002, ISBN 0-387-95443-0 .
  • The Merck Manual of Diagnosis and Therapy. Chapter 24