1-Kestose

Fig. 1 (A) Chromatographic separation of sugars. Track 1 fructose, 2 sucrose, 3 glucose, 4 mixture of the substances in tracks 1-3, 5 mixture of substances in tracks 1-3 and 6, 6 Fructo-oligosaccharides, 7 1-kestose, 8 mixture of glucose, maltose, maltotriose and maltotetraose. (B) Absorption scan of track 5 with 200 ng each substance per chromatogram zone 1 = fructosyl-nystose, 2 = nystose, 3 = 1-kestose, 4 = fructose, 5 = sucrose, 6 = glucose.

Kaempferol glucoside la 323 Kedde s reagent lb 236,237 1 -Kestose lb 423,424 6-Kestose lb 423 Ketazon lb 280 Keto acids la 262 a-Keto acids la 249,262,372 -, quinoxalone derivatives lb 343... 

Ci8H32016 0-/ -D-Fructofuranosyl-(2— l)-0-/ -D-fructofuranosyl a-D-glu-copyranoside (1-kestose) KESTOS 30 32 455 370... 

Moreover, in further studies, a genetically optimized strain of A. niger with an overexpressed /i-fructofuranosidase transformed sucrose analogues efficiently and with high yield into the 1-kestose and 1-nystose analogues functionalized with different monosaccharides of potential interest (Fig. 8).115... 

Fig. 8. Different products with sucrose analogues as substrates.115 Enzymatic synthesis of 1-kestose, 1-nystose, and their analogues by /(-fructofuranosidase of A. niger. Structures of fructo-oligosaccharides (A) commercial products, (B) mannose- (C) galactose-, and (D) xylose-substituted analogues.

The decomposition of 1-kestose is a key step in the production of fructo-oligosaccharides, which are found in many health foods because of their noncaloric and noncariogenic nature. 

Duan et al. (1994) studied the decomposition of 1-kestose (S) using /3-fructosfuranosidase (E), both in the presence and absence of the competitive inhibitor glucose (G). 

Smythe (72) observed that the trisaccharide 1-kestose (7a), which bears an additional fructose moiety bound to Cl, binds at the —b pole of the crystal of sucrose. This result implies an extended antiplanar conformation (7b) of the group Cl -C-O-C(fiructose) such that the O-C(fructose) bond (filled circles in 7b) of the additive would point toward - b, away from the crystal interior. Note that, as in the sucrose-raffinose system, the Cl -C-O-H group of sucrose 5b (filled circles) adopts a gauche conformation with the C-OH bond pointing in the +b direction. It is gratifying that the necessary extended conformation of Cl -C-O-C was later demonstrated in an X-ray crystallographic study of 1-kestose 7b (74). 

M. Verhaest, W. Lammens, K. Le Roy, C. J. De Ranter, A. Van Laere, A. Rabijns, and W. Van den Ende, Insights into the fine architecture of the active site of chicory fructan 1-exohydrolase 1-Kestose as substrate vs sucrose as inhibitor, New Phytol., 174 (2007) 90-100. 

Electron diffraction assessments of single crystals from inulin fractions indicate two antiparallel six-fold helices (Andre et al., 1996) a five-fold model has also been proposed (Marchessault et al., 1980). The hemihydrate molecule contains one water molecule for each two fructosyl units, while the monohydrate has one water molecule per fructosyl unit. When intermolecular hydrogen bonds are present, however, there is no evidence of intramolecular hydrogen bonding in the crystals. Crystal structures of 1-kestose (GF2) (Jeffrey and Park, 1972), nystose (GF3) (Jeffrey and Huang, 1993), and cycloinulohexaose (cF6) (Sawada et al., 1990) have been reported. 

Calub, T.M., Waterhouse, A.L., and Chatterton, N.J., Conformational analysis of D-fructans. I. Proton and carbon chemical-shift assignments for 1-kestose from two-dimensional NMR-spectral measurements, Carbohydrate Res., 199, 11-17, 1990. 

Jarrell, H.C., Conway, T.F., Moyna, P., and Smith, I.C.P., Manifestation of anomeric form, ring structure, and linkage in the carbon-13 NMR spectra of oligomers and polymers containing D-fructose, maltulose, isomaltulose, sucrose, leucrose, 1-kestose, nystose, inulin, and grass levan, Carbohydrate Res., 76, 45-57, 1979. 

Fructans in the Jerusalem artichoke are synthesized by the concerted action of two fructosyl transferases that were derived from invertase genes (Van Laere and Van den Ende, 2002). In the initial step (Figure 10.18), the trisaccharide 1-kestose (G-F-F) is synthesized from two sucrose molecules (G-F) in a reaction catalyzed by the enzyme sucrose sucrose fructosyl transferase (SST EC 2.4.1.99). The reaction products are 1-kestose and glucose, and the reaction is essentially irreversible due to the high free energy of hydrolysis (AG = 27.6 kJ-mok1) (Lewis, 1984). 

Kestose synthesis by 1-SST is limited by the availability of sucrose in the 0 to 100 mol m 3 range (Cairns and Ashton, 1991 Van den Ende and Van Laere, 1993). Therefore, high sucrose concentrations favor the rate of the first polymerization step and indirectly the synthesis of longer-chain-length polymers due to an elevation in 1-kestose concentration, which acts as a fructosyl donor. Glucose is converted to sucrose by sucrose synthase in the cytosol (Pollock, 1986 Wiemken et al., 1986) (Figure 10.18). 

A second enzyme, fructan fructan 1-fructosyl transferase (1-FFT EC 2.4.1.100) is responsible for chain elongation with 1-kestose and fructans with a degree of polymerization of >3 acting as... 

Dickerson, 1966 Wiemken et al., 1986). Therefore, low sucrose content is essential during fructan synthesis otherwise, 1-FFT merely transfers the fructosyl unit from 1-kestose to sucrose, forming the same products as the reactants (i.e., 1-kestose and sucrose). Both enzymes (1-SST and 1-FFT) are localized in the vacuole (Carpita et al., 1991 Darwen and John, 1989 Frehner et al., 1984). 

Fig. 8 Different products with sucrose analogues as substrates [91]. Enzymatic synthesis of levans headed with different glycopyranosides by levansucrases of different sources. 6-kestose by a Ls variant N252A, and 1-kestose, 1-nystose analogues by P-fructofuranosidase of A. niger...

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