This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis → Polysaccharides Biosynthesis|
|Biosynthesis → Cell Structures Biosynthesis → Plant Cell Structures → Primary Cell Wall|
|Biosynthesis → Cell Structures Biosynthesis → Plant Cell Structures → Secondary Cell Wall|
Some taxa known to possess this pathway include : Arabidopsis thaliana col
Cellulose is the most abundant organic polymer found in nature. It is produced by plants, some animals, algae, fungi, flagellates and bacteria such as Komagataeibacter xylinus, Agrobacterium tumefaciens and Rhizobium spp. [Ross91a]. Cellulose is an intrinsic structural component of plant primary and secondary cell walls, building a network with other carbohydrate polymers. Bacteria generally produce cellulose as an extracellular component for mechanical and chemical protection, but it can also be used to facilitate cell adhesion to host tissue [Matthysse81]. Cellulose accounts for about 20% (by weight) of the plant primary cell walls, and about 50% of the secondary cell walls.
The primary structure of cellulose is a linear array of D-glucose molecules joined by β (1,4) glycosyl linkage. The biosynthesis of cellulose is catalyzed by the cellulose synthase enzyme complex which is visualized as rosettes located in the plasma membrane. It is proposed that each rosette is composed of six subunits, and each rosette subunit in turn is composed of 6 cellulose synthases. Each individual cellulose synthase catalyzes the formation of one glucan chain which then associates with neighbor chains of the same rosette to form cellulose microfibrils [Doblin02].
In Arabidopsis the substrate for cellulose synthesis is UDP-glucose channeled from sucrose degradation. At least six cellulose synthase genes were shown to be required in cellulose synthesis in Arabidopsis. CesA1, CesA3, and CesA6 are involved in cellulose biosynthesis in the primary walls. CesA4, CesA7, and CesA8 are involved in cellulose synthesis in the secondary walls. Mutant and mutant complementation analysis indicate that these isoforms of cellulose synthase are not functionally redundant.
It was hypothesized that cellulose synthesis requires a primer, similar to glycogen biosynthesis. Recent work in cotton has shown that sitosterol-β-glucose can serve as a primer. UDP-glucose can be used to form sterol cellodextrins from sitosterol-β-glucose, presumably catalyzed by a cellulose synthase [Peng02a].
It has been shown that in addition to cellulose synthase 1,4-β-D-glucan 4-glucanohydrolase is also required in cellulose biosynthesis. It is possibly involved in trimming off defective glucans from the growing microfibrils, or cleaving off the sitosterol-β-glucose primer from the growing glucan chains [Lane01].
Unification Links: AraCyc:PWY-1001
Lane01: Lane DR, Wiedemeier A, Peng L, Hofte H, Vernhettes S, Desprez T, Hocart CH, Birch RJ, Baskin TI, Burn JE, Arioli T, Betzner AS, Williamson RE (2001). "Temperature-sensitive alleles of RSW2 link the KORRIGAN endo-1,4-beta-glucanase to cellulose synthesis and cytokinesis in Arabidopsis." Plant Physiol 126(1);278-88. PMID: 11351091
Burn02: Burn JE, Hocart CH, Birch RJ, Cork AC, Williamson RE (2002). "Functional analysis of the cellulose synthase genes CesA1, CesA2, and CesA3 in Arabidopsis." Plant Physiol 129(2);797-807. PMID: 12068120
Ha02: Ha MA, MacKinnon IM, Sturcova A, Apperley DC, McCann MC, Turner SR, Jarvis MC (2002). "Structure of cellulose-deficient secondary cell walls from the irx3 mutant of Arabidopsis thaliana." Phytochemistry 61(1);7-14. PMID: 12165296
Martin02b: Martin T, Oswald O, Graham IA (2002). "Arabidopsis seedling growth, storage lipid mobilization, and photosynthetic gene expression are regulated by carbon:nitrogen availability." Plant Physiol 128(2);472-81. PMID: 11842151
Omadjela13: Omadjela O, Narahari A, Strumillo J, Melida H, Mazur O, Bulone V, Zimmer J (2013). "BcsA and BcsB form the catalytically active core of bacterial cellulose synthase sufficient for in vitro cellulose synthesis." Proc Natl Acad Sci U S A 110(44);17856-61. PMID: 24127606
Taylor03b: Taylor NG, Howells RM, Huttly AK, Vickers K, Turner SR (2003). "Interactions among three distinct CesA proteins essential for cellulose synthesis." Proc Natl Acad Sci U S A 100(3);1450-5. PMID: 12538856
Turner97a: Turner SR, Somerville CR (1997). "Collapsed xylem phenotype of Arabidopsis identifies mutants deficient in cellulose deposition in the secondary cell wall." Plant Cell 9(5);689-701. PMID: 9165747
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