Reaction: Hydrolysis of (1→4)-β-D-xylose residues from the reducing end of oligosaccharides
Other name(s): Rex; reducing end xylose-releasing exo-oligoxylanase
Systematic name: β-D-xylopyranosyl-(1→4)-β-D-xylopyranose reducing-end xylanase
Comments: The enzyme, originally isolated from the bacterium Bacillus halodurans C-125, releases the xylose unit at the reducing end of oligosaccharides ending with the structure β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranose, leaving the new reducing end in the α configuration. It is specific for the β anomers of xylooligosaccharides whose degree of polymerization is equal to or greater than 3. The penultimate residue must be β-D-xylopyranose, but replacing either of the flanking residues with glucose merely slows the rate greatly.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 879497-03-7
References:
1. Honda, Y. and Kitaoka, M. A family 8 glycoside hydrolase from Bacillus halodurans C-125 (BH2105) is a reducing end xylose-releasing exo-oligoxylanase. J. Biol. Chem. 279 (2004) 55097-55103. [PMID: 15491996]
2. Fushinobu, S., Hidaka, M., Honda, Y., Wakagi, T., Shoun, H. and Kitaoka, M. Structural basis for the specificity of the reducing end xylose-releasing exo-oligoxylanase from Bacillus halodurans C-125. J. Biol. Chem. 2005 Feb 17 [Epub ahead of print] [PMID: 15718242]