Overview for MACiE Entry M0095

Version history

General Information

EC Number: (A member of the Isomerases, Intramolecular oxidoreductases, Interconverting aldoses and ketoses, and related compounds)

Enzyme Name: arabinose isomerase

Biological Species: Escherichia coli (Bacteria)

Catalytic Chain UniprotKB Accession Codes:

Representative PDB Code: 1fui - L-FUCOSE ISOMERASE FROM ESCHERICHIA COLI (Resolution = 2.50 Å).

Catalytic CATH Codes:

"Other" CATH Codes:

Display structure information

Overall Reaction:

Image of D-arabinose

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Image of D-ribulose


It is unknown whether this reaction is reversible or not.

Overall Comment: Two alternative mechanisms have been proposed for this reaction, the ene-diol mechanism in which two amino acid bases transfer the two protons via an ene-diol intermediate and a hydride-shift mechanisms, in which the hydrogen atom at C2 migrates as a hydride to C1. The crystal structure solved for this enzyme suggest the ene-diol mechanism due to the presence of the Asp361 and Glu337 which can act as the general acid/base residues [1].

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Stepwise Description of the Reaction

Step 1Asp361 deprotonates the C1 alcohol of the sugar, initiating ring-opening. The C5 oxygen deprotonates water.
Step 2Glu337 deprotonates the C2 carbon, initiating double bond rearrangement to form the enol-form of the substrate. The newly formed oxyanion deprotonates Asp361.
Step 3Asp361 deprotonates the C2 alcohol, initiating double bond rearrangement, and the C1 atom deprotonates Glu337 to re-form the keto-form of the substrate.
Step 4In an inferred return step, water deprotonates Asp361 to regenerate the enzyme active site.
Step 5Ring closing to form the ribulose product is assumed to occur outside of the enzyme active site.

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Catalytic Residues Involved

Type Number Chain Location of Function
Glu 337 A Side Chain
Asp 361 A Side Chain

Metal Cofactors for M0095

Type Het group Number Chain
manganese MN 1 A Overview


  1. J. E. Seemann et al. (1997), J. Mol. Biol., 273, 256-268. Structure and mechanism of L-fucose isomerase from Escherichia coli.
    Medline: 9367760
  2. C. A. Collyer et al. (1990), Proc. Natl Acad. Sci. USA, 87, 1362-1366. Observations of reaction intermediates and the mechanism of aldose-ketose interconversion by D-xylose isomerase.
    Medline: 2304904

Homologue information for M0095 (1fui)

CSA Homologues

MACiE Homologues (within the PDB)

MACiE Homologues (within UniprotKB/SwissProt)

Links to this entry in other databases

Link to EC-PDB-SUM Link to PDB-SUM Link to RCSB PDB Link to PDBe Link to CSA
Link to MetaCyc Link to KEGG Link to BRENDA Link to ExplorENZ
Link to EzCatDB

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cytoplasm (cellular component)
monosaccharide metabolic process (biological process)
fucose metabolic process (biological process)
L-fucose isomerase activity (molecular function)
intramolecular oxidoreductase activity, interconverting aldoses and ketoses (molecular function)
fucose catabolic process (biological process)
manganese ion binding (molecular function)