| 词条 | Cellulose synthase (UDP-forming) |
| 释义 |
| Name = Cellulose synthase (UDP-forming) | EC_number = 2.4.1.12 | CAS_number = 9027-19-4 | IUBMB_EC_number = 2/4/1/12 | GO_code = | image =Structure of a bacterial cellulose synthase.png | width = | caption =Structure of a bacterial cellulose synthase |name=}}{{Infobox protein family | Symbol = BCS | Name = Cellulose synthase | image = | width = | caption = | Pfam = PF03170 | Pfam_clan = | InterPro = IPR018513 | SMART = | PROSITE = | MEROPS = | SCOP = | TCDB = | OPM family = 302 | OPM protein = 4p02 | CAZy = | CDD = | Membranome superfamily = 539 }} In enzymology, a cellulose synthase ({{EC number|2.4.1.12}}, UDP-glucose:(1→4)-β-D-glucan 4-β-D-glucosyltransferase) is an enzyme that catalyzes the chemical reaction UDP-glucose + [(1→4)-β-D-glucosyl]n = UDP + [(1→4)-β-D-glucosyl]n+1 Thus, the two substrates of this enzyme are UDP-glucose and [(1→4)-β-D-glucosyl]n, whereas its two products are UDP and [(1→4)-β-D-glucosyl]n+1. This enzyme is involved in the synthesis of cellulose. A similar enzyme utilizes GDP-glucose, cellulose synthase (GDP-forming) (EC 2.4.1.29). CelluloseCellulose is an aggregation of unbranched polymer chains made of β-(1→4)-linked glucose residues that makes up a large portion of primary and secondary cell walls.[1][2][3][4] Although important for plants, it is also synthesized by most algae, some bacteria, and some animals.[5][6][7][8] Worldwide, 2 × 1011 tons of cellulose microfibrils are produced,[9] which serves as a critical source of renewable biofuels and other biological-based products, such as lumber, fuel, fodder, paper and cotton.[2][10]Purpose of celluloseThese microfibrils are made on the surface of cell membranes to reinforce cells walls, which has been researched extensively by plant biochemists and cell biologist because 1) they regulate cellular morphogenesis and 2) they serve alongside many other constituents (i.e. lignin, hemicellulose, pectin) in the cell wall as a strong structural support and cell shape.[10] Without these support structures, cell growth would cause a cell to swell and spread in all directions, thus losing its shape viability [11] Cellulose synthase structurePlant cellulose synthases belong to the family of glycosyltransferases, which are proteins involved in the biosynthesis and hydrolysis of the bulk of earth's biomass.[12] Cellulose is synthesized by large cellulose synthase complexes (CSCs), which consist of synthase protein isoforms (CesA) that are arranged into a unique hexagonal structure known as a “particle rosette” 50 nm wide and 30–35 nm tall.[6][13][14] There are more than 20 of these full-length integral membrane proteins, each of which is around 1000 amino acids long.[2][3] These rosettes, formerly known as granules, were first discovered in 1972 by electron microscopy in green algae species Cladophora and Chaetomorpha[15] (Robinson et al. 1972). Solution x-ray scattering have shown that CesAs are at the surface of a plant cell and are elongated monomers with a two catalytic domains that fuse together into dimers. The center of the dimers is the main point of catalytic activity.[6] Since cellulose is made in all cell walls, CesA proteins are present in all tissues and cell types of plants. Nonetheless, there are different types of CesA, some tissue types may have varying concentrations of one over another. For example, the AtCesA1 (RSW1) protein is involved in the biosynthesis of primary cell walls throughout the whole plant while the AtCesA7 (IRX3) protein is only expressed in the stem for secondary cell wall production.[16] Cellulose synthase activityCellulose biosynthesis is the process during which separate homogeneous β-(1→4)-glucan chains, ranging from 2,000 to 25,000 glucose residues in length, are synthesized and then immediately hydrogen bond with one another to form rigid crystalline arrays, or microfibrils.[2] Microfibrils in the primary cell wall are approximately 36 chains long while those of the secondary cell wall are much larger, containing up to 1200 β-(1→4)-glucan chains.[10][16] Uridine diphosphate-glucose (UDP), which is produced by the enzyme sucrose synthase (SuSy) that produces and transports UDP-glucose to the plasma membrane is the substrate used by cellulose synthase to produce the glucan chains.[2][17] The rate at which glucose residues are synthesized per one glucan chain ranges from 300 to 1000 glucose residues per minute, the higher rate being more prevalent in secondary wall particles, such as in the xylem.[18][19] Supporting structuresMicrofibril synthesis is guided by cortical microtubules, which lie beneath the plasma membrane of elongating cells, in that they form a platform on which the CSCs can convert glucose molecules into the crystalline chains. The microtubule–microfibril alignment hypothesis proposes that cortical microtubules, which lie beneath the plasma membrane of elongating cells, provide tracks for CSCs that convert glucose molecules into crystalline cellulose microfibrils.[20] The direct hypothesis postulates some types of direct linkage between CESA complexes and microtubules.[17] Additionally, the KORRIGAN (KOR1) protein is thought to be a critical component of cellulose synthesis in that it acts as a cellulase at the plasma membrane-cell wall interface. KOR1 interacts with a two specific CesA proteins, possibly by proof-reading and relieving stress created by glucan chain synthesis, by hydrolyzing disordered amorphous cellulose.[21] Environmental influencesCellulose synthesis activity is affected by many environmental stimuli, such as hormones, light, mechanical stimuli, nutrition, and interactions with the cytoskeleton. Interactions with these factors may influence cellulose deposition in that it affects the amount of substrate produced and the concentration and/or activity of CSCs in the plasma membrane.[2][6] References1. ^{{cite journal | vauthors = Campbell JA, Davies GJ, Bulone V, Henrissat B | title = A classification of nucleotide-diphospho-sugar glycosyltransferases based on amino acid sequence similarities | journal = The Biochemical Journal | volume = 326 ( Pt 3) | issue = 3 | pages = 929–39 | date = September 1997 | pmid = 9334165 | pmc = 1218753 | doi = 10.1042/bj3260929u }} 2. ^1 2 3 4 5 {{cite journal | vauthors = Olek AT, Rayon C, Makowski L, Kim HR, Ciesielski P, Badger J, Paul LN, Ghosh S, Kihara D, Crowley M, Himmel ME, Bolin JT, Carpita NC | title = The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers | journal = The Plant Cell | volume = 26 | issue = 7 | pages = 2996–3009 | date = July 2014 | pmid = 25012190 | doi = 10.1105/tpc.114.126862 | pmc = 4145127 }} 3. ^1 {{cite journal | vauthors = Richmond T | title = Higher plant cellulose synthases | journal = Genome Biology | volume = 1 | issue = 4 | pages = REVIEWS3001 | date = 2000 | pmid = 11178255 | pmc = 138876 | doi = 10.1186/gb-2000-1-4-reviews3001 }} 4. ^{{cite journal | vauthors = Lei L, Li S, Gu Y | title = Cellulose synthase complexes: composition and regulation | journal = Frontiers in Plant Science | volume = 3 | pages = 75 | date = 2012 | pmid = 22639663 | pmc = 3355629 | doi = 10.3389/fpls.2012.00075 }} 5. ^{{cite journal | vauthors = Nakashima K, Yamada L, Satou Y, Azuma J, Satoh N | title = The evolutionary origin of animal cellulose synthase | journal = Development Genes and Evolution | volume = 214 | issue = 2 | pages = 81–8 | date = February 2004 | pmid = 14740209 | doi = 10.1007/s00427-003-0379-8 }} 6. ^1 2 3 {{cite journal | vauthors = Yin Y, Huang J, Xu Y | title = The cellulose synthase superfamily in fully sequenced plants and algae | journal = BMC Plant Biology | volume = 9 | pages = 99 | date = July 2009 | pmid = 19646250 | pmc = 3091534 | doi = 10.1186/1471-2229-9-99 }} 7. ^{{cite journal | vauthors = Sethaphong L, Haigler CH, Kubicki JD, Zimmer J, Bonetta D, DeBolt S, Yingling YG | title = Tertiary model of a plant cellulose synthase | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 110 | issue = 18 | pages = 7512–7 | date = April 2013 | pmid = 23592721 | pmc = 3645513 | doi = 10.1073/pnas.1301027110 }} 8. ^{{cite journal|last1=Li, Lei, Gu|first1=S, L, Y|title=Functional analysis of complexes with mixed primary and secondary cellulose synthases|journal=Plant Signaling and Behavior|date=2012|volume=8|page=23179|url=http://www.pubfacts.com/detail/23299322/Functional-analysis-of-complexes-with-mixed-primary-and-secondary-cellulose-synthases.}} 9. ^{{cite book|last1=Lieth|first1=H|title=Measurement of calorific values. Primary productivity of the biosphere|volume=14|date=1975|publisher=Springer|location=New York|pages=119–129|doi=10.1007/978-3-642-80913-2|series=Ecological Studies|isbn=978-3-642-80915-6}} 10. ^1 2 {{cite journal | vauthors = Cutler S, Somerville C | title = Cloning in silico | journal = Current Biology | volume = 7 | issue = 2 | pages = R108–11 | date = February 1997 | pmid = 9081659 | doi = 10.1016/S0960-9822(06)00050-9 | url = https://www.researchgate.net/publication/222946544 }} 11. ^{{cite journal | vauthors = Hogetsu T, Shibaoka H | title = Effects of colchicine on cell shape and on microfibril arrangement in the cell wall of Closterium acerosum | journal = Planta | volume = 140 | issue = 1 | pages = 15–8 | date = January 1978 | pmid = 24414355 | doi = 10.1007/BF00389374 }} 12. ^{{cite journal | vauthors = Campbell JA, Davies GJ, Bulone V, Henrissat B | title = A classification of nucleotide-diphospho-sugar glycosyltransferases based on amino acid sequence similarities | journal = The Biochemical Journal | volume = 329 (Pt 3) | pages = 719 | date = February 1998 | pmid = 9445404 | pmc = 1219098 }} 13. ^{{cite journal|last1=Giddings, Brower, Staehelin|first1=TH, DL, LA|title=formation of cellulose fibrils in primary and secondary walls|journal=Journal of Cellular Biology|date=1980|volume=84|issue=2|pages=327–339|doi=10.1083/jcb.84.2.327}} 14. ^{{cite journal | vauthors = Bowling AJ, Brown RM | title = The cytoplasmic domain of the cellulose-synthesizing complex in vascular plants | journal = Protoplasma | volume = 233 | issue = 1–2 | pages = 115–27 | date = 2008 | pmid = 18709477 | doi = 10.1007/s00709-008-0302-2 }} 15. ^{{cite journal | vauthors = Robinson DG, White RK, Preston RD | title = Fine structure of swarmers of Cladophora and Chaetomorpha : III. Wall synthesis and development | journal = Planta | volume = 107 | issue = 2 | pages = 131–44 | date = June 1972 | pmid = 24477398 | doi = 10.1007/BF00387719 }} 16. ^1 {{cite journal | vauthors = Richmond T | title = Higher plant cellulose synthases | journal = Genome Biology | volume = 1 | issue = 4 | pages = REVIEWS3001 | date = 2000 | pmid = 11178255 | doi = 10.1186/gb-2000-1-4-reviews3001 }} 17. ^1 {{cite journal|last1=Heath|first1=IB|title=A unified hypothesis for the role of membrane bound enzyme complexes and microtubules in plant cell wall synthesis|journal=Journal of Theoretical Biology|date=1974|volume=48|issue=2|pages=445–449|doi=10.1016/S0022-5193(74)80011-1|url=https://www.researchgate.net/publication/18705609}} 18. ^{{cite journal | vauthors = Paredez AR, Somerville CR, Ehrhardt DW | title = Visualization of cellulose synthase demonstrates functional association with microtubules | journal = Science | volume = 312 | issue = 5779 | pages = 1491–5 | date = June 2006 | pmid = 16627697 | doi = 10.1126/science.1126551 }} 19. ^{{cite journal | vauthors = Wightman R, Turner SR | title = The roles of the cytoskeleton during cellulose deposition at the secondary cell wall | journal = The Plant Journal | volume = 54 | issue = 5 | pages = 794–805 | date = June 2008 | pmid = 18266917 | doi = 10.1111/j.1365-313X.2008.03444.x }} 20. ^{{cite journal | vauthors = Green PB | title = Mechanism for Plant Cellular Morphogenesis | journal = Science | volume = 138 | issue = 3548 | pages = 1404–5 | date = December 1962 | pmid = 17753861 | doi = 10.1126/science.138.3548.1404 }} 21. ^{{cite journal | vauthors = Mansoori N, Timmers J, Desprez T, Alvim-Kamei CL, Kamei CL, Dees DC, Vincken JP, Visser RG, Höfte H, Vernhettes S, Trindade LM | title = KORRIGAN1 interacts specifically with integral components of the cellulose synthase machinery | journal = PLOS One | volume = 9 | issue = 11 | pages = e112387 | date = 2014 | pmid = 25383767 | pmc = 4226561 | doi = 10.1371/journal.pone.0112387 }} Further reading{{refbegin}}
2 : EC 2.4.1|Enzymes of known structure |
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