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

Paper ID Volume ID Publish Year Pages File Format Full-Text
3534 174 2012 9 PDF Available
Title
Enzyme kinetics and identification of the rate-limiting step of enzymatic arabinoxylan degradation
Abstract

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 3.2.1.55), one derived from Aspergillus niger (AFAn) and one from Bifidobacterium adolescentis (AFBa), respectively, a β-xylosidase (EC 3.2.1.37) from Trichoderma reesei, and an engineered D11F/R122D variant of Bacillus subtilis XynA endo-1,4-β-xylanase (EC 3.2.1.8) 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 30 min, 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.

► Wheat arabinoxylan was treated with designed combinations of pure enzymes. ► Endo-1,4β-xylanase was rate-limiting for enzymatic xylose release from arabinoxylan. ► A probability calculation is proposed for quantitation of β-xylosidase attack.

Keywords
Arabinoxylan hydrolysis; Enzyme kinetics; α-l-Arabinofuranosidase; β-Xylosidase; Endo-xylanase; SynergyAFAn, α-l-arabinofuranosidase GH 51 derived from Aspergillus niger; AFBa, α-l-arabinofuranosidase GH 43 derived from Bifidobacterium adolescentis; BX, β
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Enzyme kinetics and identification of the rate-limiting step of enzymatic arabinoxylan degradation
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biochemical Engineering Journal - Volume 69, 15 December 2012, Pages 8–16
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us