Overview for MACiE Entry M0095
EC Number: 184.108.40.206 (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
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 .
View similar reactions
Stepwise Description of the Reaction
|Step 1||Asp361 deprotonates the C1 alcohol of the sugar, initiating ring-opening. The C5 oxygen deprotonates water.|
|Step 2||Glu337 deprotonates the C2 carbon, initiating double bond rearrangement to form the enol-form of the substrate. The newly formed oxyanion deprotonates Asp361.|
|Step 3||Asp361 deprotonates the C2 alcohol, initiating double bond rearrangement, and the C1 atom deprotonates Glu337 to re-form the keto-form of the substrate.|
|Step 4||In an inferred return step, water deprotonates Asp361 to regenerate the enzyme active site.|
|Step 5||Ring closing to form the ribulose product is assumed to occur outside of the enzyme active site.|
View similar reactions (composite manual annotation)
Catalytic Residues Involved
||Location of Function
Metal Cofactors for M0095
- J. E. Seemann et al. (1997), J. Mol. Biol., 273, 256-268. Structure and mechanism of L-fucose isomerase from Escherichia coli.
- 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.
Homologue information for M0095 (1fui)
MACiE Homologues (within the PDB)
MACiE Homologues (within UniprotKB/SwissProt)
Links to this entry in other databases