Enzyme kinetics and identification of the rate-limiting step of enzymatic arabinoxylan degradation

Louise Enggaard Rasmussen, Cheng Xu, Jens Sørensen, Michael Krogsgaard Nielsen, Anne S. Meyer

Research output: Contribution to journalJournal articleResearchpeer-review


This study investigated the kinetics of multi-enzymatic degradation of soluble wheat arabinoxylan by monitoring the release of xylose and arabinose during designed treatments with mono-component enzymes at different substrate concentrations. The results of different combinations of α-l-arabinofuranosidases (EC, one derived from Aspergillus niger (AFAn) and one from Bifidobacterium adolescentis (AFBa), respectively, a β-xylosidase (EC from Trichoderma reesei, and an engineered D11F/R122D variant of Bacillus subtilis XynA endo-1,4-β-xylanase (EC were examined. The two selected α-l-arabinofuranosidases catalyze liberation of arabinose residues linked 1→3 to singly (AFAn) or doubly (AFBa) substituted xyloses in arabinoxylan, respectively. When added to arabinoxylan at equimolar levels, the AFBa enzyme catalyzed the release of more arabinose, i.e. had a higher rate constant than AFAn, but with respect to the xylose release, AFAn – as expected – exhibited a better synergistic effect than AFBa with β-xylosidase. This synergistic effect with AFAn was estimated to increase the number of β-xylosidase catalyzed cuts from ∼3 (with β-xylosidase alone) to ∼7 in each arabinoxylan substrate molecule. However, the synergistic effects between β-xylosidase and the α-l-arabinofuranosidases on the xylose release were low as compared to the effect of xylanase addition with β-xylosidase, which increased the xylose release by ∼25 times in 30min, to a yield equivalent to ∼104 β-xylosidase catalyzed cuts in each arabinoxylan substrate molecule. At equimolar addition levels of the four enzymes, the xylanase activity was thus rate-limiting for the β-xylosidase catalyzed depolymerization to release xylose from arabinoxylan. The work provides clues to design efficient enzymatic degradation of arabinoxylan into fermentable monosaccharides.

Original languageEnglish
JournalBiochemical Engineering Journal
Pages (from-to)8-16
Publication statusPublished - 2012


  • Arabinoxylan hydrolysis
  • Enzyme kinetics
  • β-l-Arabinofuranosidase
  • β-Xylosidase
  • Endo-xylanase
  • Synergy


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