turanose and leucrose

In the daily diet, sweeteners play an indispensable role. Among them, sucrose, a widely occurring disaccharide in nature, is a commonly used sweetener. However, the intake of sucrose can cause a rapid increase in blood glucose, which leads to a number of health problems. Therefore, there is an urgent need for possible alternatives to sucrose. Currently, four naturally occurring sucrose isomers, trehalulose, turanose, leucrose, and isomaltulose are considered to be possible alternatives to sucrose due to their suitable sweetness, potential physiological benefits, and feasible production processes. This review covers the properties of these alternative sweeteners, including their structure, sweetness, hydrolysis rate, toxicology, and cariogenicity, and exhibits their potential applications in chronic diseases management, anti-inflammatory supplement, prebiotic dietary supplement, and stabilizing agent. The biosynthesis of these sucrose isomers using carbohydrate-active enzymes and their industrial production processes are also systematically summarized.

Topics: Diet; Disaccharides; Food; Humans; Isomaltose; Isomerism; Sucrose; Sweetening Agents; Taste

Trehalose supports the growth of Thermus thermophilus strain HB27, but the absence of obvious genes for the hydrolysis of this disaccharide in the genome led us to search for enzymes for such a purpose. We expressed a putative alpha-glucosidase gene (TTC0107), characterized the recombinant enzyme, and found that the preferred substrate was alpha,alpha-1,1-trehalose, a new feature among alpha-glucosidases. The enzyme could also hydrolyze the disaccharides kojibiose and sucrose (alpha-1,2 linkage), nigerose and turanose (alpha-1,3), leucrose (alpha-1,5), isomaltose and palatinose (alpha-1,6), and maltose (alpha-1,4) to a lesser extent. Trehalose was not, however, a substrate for the highly homologous alpha-glucosidase from T. thermophilus strain GK24. The reciprocal replacement of a peptide containing eight amino acids in the alpha-glucosidases from strains HB27 (LGEHNLPP) and GK24 (EPTAYHTL) reduced the ability of the former to hydrolyze trehalose and provided trehalose-hydrolytic activity to the latter, showing that LGEHNLPP is necessary for trehalose recognition. Furthermore, disruption of the alpha-glucosidase gene significantly affected the growth of T. thermophilus HB27 in minimal medium supplemented with trehalose, isomaltose, sucrose, or palatinose, to a lesser extent with maltose, but not with cellobiose (not a substrate for the alpha-glucosidase), indicating that the alpha-glucosidase is important for the assimilation of those four disaccharides but that it is also implicated in maltose catabolism.

Topics: alpha-Glucosidases; Bacterial Proteins; Disaccharides; Isomaltose; Kinetics; Maltose; Mutagenesis, Site-Directed; Phenotype; Recombinant Proteins; Substrate Specificity; Sucrose; Thermus thermophilus; Trehalose

Not only sucrose but the five isomeric alpha-D-glucosyl-D-fructoses trehalulose, turanose, maltulose, leucrose, and palatinose are utilized by Klebsiella pneumoniae as energy sources for growth, thereby undergoing phosphorylation by a phosphoenolpyruvate-dependent phosphotransferase system uniformly at 0-6 of the glucosyl moiety. Similarly, maltose, isomaltose, and maltitol, when exposed to these conditions, are phosphorylated regiospecifically at O-6 of their non-reducing glucose portion. The structures of these novel compounds have been established unequivocally by enzymatic analysis, acid hydrolysis, FAB negative-ion spectrometry, and 1H and 13C NMR spectroscopy. In cells of K. pneumoniae, hydrolysis of sucrose 6-phosphate is catalyzed by sucrose 6-phosphate hydrolase from Family 32 of the glycosylhydrolase superfamily. The five 6'-O-phosphorylated alpha-D-glucosyl-fructoses are hydrolyzed by an inducible (approximately 49-50 Kda) phospho-alpha-glucosidase from Family 4 of the glycosylhydrolase superfamily.

Topics: alpha-Glucosidases; Amino Acid Sequence; beta-Fructofuranosidase; Carbohydrate Conformation; Chromatography, Thin Layer; Disaccharides; Fructose; Glycoside Hydrolases; Hydrolysis; Immunoblotting; Isomaltose; Isomerism; Klebsiella pneumoniae; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Molecular Structure; Phosphorylation; Sucrose

Dispirodioxanyl pseudotetrasaccharides 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 6-O-alpha-D-glucopyranosyl-beta-D-fructofuranose 1,2':2,1'-dianhydride, 5-O-alpha-D-glucopyranosyl-alpha-D-fructopyranose 5-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, 4-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 4-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, 4-O-beta-D-galactopyranosyl-alpha-D-fructofuranose 4-O-beta-D-galactopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, and 3-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 3-O-alpha-D-glucopyranosyl-beta-D-fructofuranose 1,2':2,1'-dianhydride were respectively obtained, on a preparative scale, by dissolution of the isomeric glycosylfructoses palatinose, leucrose, maltulose, lactulose, and turanose in anhydrous hydrogen fluoride. The reaction, involving selective protonation at the free anomeric position of the fructose unit, was extended to the preparation of the pseudotrisaccharides 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose beta-D-fructopyranose 1,2':2',1-dianhydride from palatinose and fructose, and to its 3-O-, 4-O-, and 4'-O-glucosyl analogues using turanose and maltulose as the disaccharide precursor. The cross-reactions of palatinose with maltulose and with leucrose resulted in the preparation of 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 4-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride and 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 5-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, respectively.

Topics: Anhydrides; Carbohydrate Sequence; Dioxanes; Disaccharides; Hydrofluoric Acid; Isomaltose; Isomerism; Lactulose; Molecular Sequence Data; Oligosaccharides; Protons

Selective activation of the ketose unit in the isomeric glycosylfructoses, palatinose, leucrose, maltulose, turanose and lactulose, with pyridinium poly(hydrogen fluoride) resulted in the almost quantitative formation of glycosylated difructose dianhydrides. The reaction preferentially involves a reactive fructofuranosyl oxocarbenium ion and is subject to stereoelectronic control. The relative amounts of isomeric spirodioxanyl oligosaccharides obtained within a series was shown to depend on the reaction conditions, especially on the hydrogen fluoride-pyridine ratio. Using suitable concentrations of hydrogen fluoride in pyridine, the reaction was easily directed to the formation of the kinetic difuranosyl or thermodynamic pyranosyl derivatives. More rigorous conditions resulted in the specific hydrolysis of one glycosidic bond in the tetrasaccharides derived from palatinose, leucrose and turanose, to yield spirodioxanyl trisaccharides.

Topics: Anhydrides; Carbohydrate Sequence; Disaccharides; Fructose; Hydrofluoric Acid; Isomaltose; Lactulose; Molecular Sequence Data; Oligosaccharides; Protons; Pyridinium Compounds; Stereoisomerism