Fructans structure

Tungland, B.C., Fructooligosaccharides and other fructans structures and occurrence, production, regulatory aspects, food applications, and nutritional health significance, ACS Symp. Ser., 849, 135-152, 2003. 

Arrizon, J., Morel, S., Gschaedler, A. and Monsan, P. (2010) Comparison of the water-soluble carbohydrate composition and fructan structures of Agave tequilana plants of different ages. Food Chem., 122, 123-130. 

From sedimentation and diffusion measurements, Ogston has determined the molecular weight of the fructans from both leafy cocksfoot grass (Dacty-lis glomerata) and Italian rye grass (Lolium italicum) to be 5,500.261 Both polysaccharides were polymolecular, and the data indicated a singly-branched structure for each. 

Polymers of D-fructose are important carbohydrate reserves in a number of plants. Inulins and levans are two major types that differ in structure. D-Fructans require only relatively mild conditions for their hydrolysis, for example, levan was qualitatively hydrolyzed by hot, dilute, aqueous oxalic acid. Permethylated fructans could be hydrolyzed with 2 M CF3CO2H for 30 min at 60°. Fructan oligosaccharides were hydrolyzed in dilute sulfuric acid (pH 2) at 70 (see Ref. 53) or 95° (0.1 M). D-Fructans from timothy haplocorm (where they comprise 63% of the water-soluble carbohydrates) could be hydrolyzed with 0.01 M hydrochloric acid at 98°. 

X-ray crystal structure analysis showed no crystallinity. Fructan is amorphous. X-ray analysis was performed on a General Electric X-ray diffraction refractometer. 

Structure. The nmr spectra, shown in Figure 2, indicates that essentially all fructose molecules in the polymers are in the same conformation. In Table I, nmr peaks from fructan are compared to peaks from known inulin 0-(l->2) linked) and bacterial levan (P-(2->6) linked). Data clearly show the fructan to be of the p-(2- 6) type (27). (Sec Table II.)... 

Fructans are polysaccharides composed of o-fructofuranose units. They are important in short-term energy reserves for grasses and some plants. Inulin, found in dahlias, and levans from grasses are examples of fructans. Levans are short linear polysaccharides composed of (3 2 1 linked fructose units as illustrated in structure 9.21. 

The term inulin first appeared in the literature in 1818 (Thomson, 1818), predating the discovery of fructose by about 30 years. It was ascribed to a substance, first isolated from elecampagne (Inula helenium L.) in 1804 (Rose, 1804). Jerusalem artichoke was first recorded as a source of inulin in around 1870. The actual linear structure of the molecule was not elucidated until the 1950s, and the small degree of branching that can occur only in the mid-1990s (De Leenheer and Hoebregs, 1994). As a polymer of fructose, inulin is classified as a fructan of which there are several types... 

Bomet, F.R.J., Fructo-oligosaccharides and other fructans chemistry, structure and nutritional effects, in Advanced Dietary Fibre Technology, McCleary, B.V. and Prosky, L., Eds., Blackwell Science, Oxford, 2001, pp. 480 193. 

Tuber structure in cross section from exterior to interior can be separated into the epidermis, cortex, outer medulla, inner medulla, and pith (Mazza, 1985). Relatively little is known about the temporal sequence of cell division and differentiation leading up to bulking. Sink capacity is a function of the combined vacuolar volume of the tubers, the location of fructan synthesis and storage within the cells (Darwen and John, 1989 Keller et al., 1988 Pollock, 1986). Vacuolar volume is a function of cell size and number. The size of individual cells within the tuber varies with tissue type cortex (286 cells per 10 mm2), extension zone (145 cells per 10 mm2), storage tissue (85 cells per 10 mm2), and pith (149 cells per 10 mm2) (Schubert and Feuerle, 1997). The extent that cell number and size increases after the initial formation of the tuber has not been adequately documented. 

Carpita, N.C., Kanabur, J., and Housley, T.L., Linkage structure of fructans and fructan oligomers from Triticum aestivum and Festuca arundinacea leaves, J. Plant Physiol., 134, 62-168, 1989. 

The spores of Aspergillus sydowi contain an enzyme system that converts sucrose into a fructan having a structure comparable to that of inulin. The polysaccharide is cleaved by )8-D-(2 1)-fruc-tanases, whereas it is unaffected by /3-D-(2 6)-fructanases. Oligo-... 

Inulin, levan, graminan, phlein, andkestoses are classified as fructans [12]. Inulin exists either as a linear, branched, or cyclic fructan whereas the structure of the remaining fructans are linear and branched (O Table 2) [13]. 

A variety of polysaccharides with less common structure, although they contain mainly D-glucopyranosyl (glucans) or fructofuranosyl (fructans) groups, were isolated from plants [62]. Some of these are indicated in Table 7.7.1. 

This obvious structural difference between plant and bacterial inulin has its origin in the individual synthesis related system. Feedstock for both inulins is sucrose. However, the plant inulin production is a two-step reaction, starting with a sucrose-1-fructosyltransferase (1-SST). One sucrose molecule acts as donor and a second one as acceptor of a fructosyl unit. This leads to the formation of the trisaccharide 1-kestose. Catalyzed by a fructan-fructan-1-fructosyltransferase (1-FFT), fructosyl units are shuffled between the 1-kestose and higher polymeric p-(2 1) linked fructan molecules in the second step. Repetition of this step results in inulin with (3-(2 1) linkages only [129-132]. 

Phleins, Levans and Fructans. The strictly p-(2- 6)-linked polymer of fructofuranoside units attached to sucrose is termed phlein. There appear to be no experimental investigations of its structure, although some theoretical work with the primitive AMI basis set suggested a helix for the p-(2- 6)-linked fructofuranose heptamer. ... 

Bacillus subtilis levansucrase (sucrose 2,6-/8-D-fructan 6-)8-D-fructosyltrans-ferase, EC 2.4.1.10) catalyzes fructosyl transfer from sucrose to levan (154). In the absence of a fructosyl acceptor, the primary reaction is sucrose hydrolysis, although a limited amount of self-initiated levan synthesis occurs as well (155). As with sucrose phosphorylase, acceptor specificity is broad a number of saccharides and other nucleophiles are suitable fructosyl acceptors (154-158). The complete amino acid sequence of the approximately SO-kDa enzyme has been determined by both protein (159) and gene (160) sequence analyses. The three-dimensional structure at 3.8 A reveals a rod- or ellipsoid-shaped protein with a length some four times the diameter (161). 

Fructose occurs rarely in the bacterial polysaccharide. It has been found in the LPS of several Vibrio species [108] and in the K4 [109] and Kll [110] capsular antigens of Escherichia coli. In all cases, fructose appears as a terminal residue. In several plant species, fructans consisting of p-D-fructofuranosyl units are present as important storage polymers. The structure of the polysaccharide isolated from B. caryophylli is different from those of the above polysaccharides however, as levan can be isolated as bacterial exopolysaccharides, this polysaccharide may be a side-product of levan biosynthesis. 

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