MetaCyc Compound Class: D-fructose

Synonyms: fructose, laevosan, levugen, laevoral, fructosteril, levulose, fru, fru-ring, D-fructose-ring, D-fructose

Superclasses: all carbohydratesa carbohydratea glycana sugara monosaccharidea hexosea D-hexose
all carbohydratesa carbohydratea glycana sugara monosaccharidea hexosefructose

Fructose is a 6-carbon polyhydroxyketone. When dissolved in solution fructose forms one of two ring structures - the 5-member ring D-fructofuranoseand the 6-member ring D-fructopyranose. Mixtures at equilibrium contain 70% fructopyranose and 30% fructofuranose.

A homopolymeric form of fructose is called a fructan, and can be formed by β(2->1) or β(2->6) glycosidic bonds between fructose molecules.

Child Classes: D-fructofuranose (3), D-fructopyranose (2)


Unification Links: CAS:57-48-7, CAS:30237-26-4, ChEBI:15824, IAF1260:33835, KEGG:C00095

Reactions known to produce the compound:

Not in pathways:
a protopanaxatriol-type ginsenoside with two glycosyl residues at position 6 + 2 H2O → a protopanaxatriol-type ginsenoside with no glycosidic modification at position 6 + a monosaccharide + D-glucopyranose
a protopanaxadiol-type ginsenoside with two glycosyl residues at position 20 + H2O → a protopanaxadiol-type ginsenoside with a single glucosyl residue at position 20 + a monosaccharide

Not in pathways:
a thioglucoside + H2O → a sugar + a thiol
a sugar phosphate + H2O → a sugar + phosphate
glycosyl-N-acylsphingosine + H2O → a ceramide + a sugar

In Reactions of unknown directionality:

Not in pathways:
a D-hexose + an acyl phosphate = a D-hexose-phosphate + a carboxylate
a D-hexose + ATP = D-hexose 6-phosphate + ADP + H+
phosphoramidate + a D-hexose = an α-hexose 1-phosphate + ammonium

Not in pathways:
a protopanaxatriol-type ginsenoside with two glycosyl residues at position 6 + H2O = a protopanaxatriol-type ginsenoside with a single glucosyl at position 6 + a monosaccharide

In Transport reactions:
a [PTS enzyme I]-Nπ-phospho-L-histidine + D-fructose[periplasm] → D-fructose 1-phosphate[cytosol] + a [PTS enzyme I]-L-histidine,
a monosaccharide[extracellular space] + ATP + H2O ↔ a monosaccharide[cytosol] + ADP + phosphate,
a [PTS enzyme I]-Nπ-phospho-L-histidine + a sugar[out] → a [PTS enzyme I]-L-histidine + a sugar phosphate[in]

Enzymes inhibited by D-fructose, sorted by the type of inhibition, are:

Inhibitor (Competitive) of: trehalose-6-phosphate hydrolase [Gotsche95] Inhibitor (Mechanism unknown) of: sucrose synthase [morellM85], fructokinase [Baysdorfer89], fructokinase [Baysdorfer89] Inhibitor (Other types) of: fructokinase [MartinezBarajas97], fructokinase [MartinezBarajas96], fructokinase [MartinezBarajas96]

This compound has been characterized as an alternative substrate of the following enzymes: N-acetylglucosamine kinase, fucose:H+ symporter, NAD-xylitol dehydrogenase, L-sorbosone dehydrogenase, mannokinase, L-rhamnulose kinase, maltose O-acetyltransferase, D-gluconate 5-dehydrogenase


Baysdorfer89: Baysdorfer C., Kremer D.F., Sicher R.C. "Partial purification and characterization of fructokinase activity from Barley leaves." J. Plant Physiol. (1989) 134:156-161.

Gotsche95: Gotsche S, Dahl MK (1995). "Purification and characterization of the phospho-alpha(1,1)glucosidase (TreA) of Bacillus subtilis 168." J Bacteriol 177(10);2721-6. PMID: 7751281

MartinezBarajas96: Martinez-Barajas E., Randall D.D. "Purification and characterization of fructokinase from developing tomato (Lycopersicon esculentum Mill.) fruits." Planta (1996) 199:451-458.

MartinezBarajas97: Martinez-Barajas E, Krohn BM, Stark DM, Randall DD (1997). "Purification and characterization of recombinant tomato fruit (Lycopersicon esculentum Mill.) fructokinase expressed in Escherichia coli." Protein Expr Purif 11(1);41-6. PMID: 9325137

morellM85: morell M., Copeland L. "Sucrose synthase of Soybean nodules." Plant Physiol. (1985) 78:149-154.

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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