Abstract
BackgroundArabinan is an important plant polysaccharide degraded mainly by two hydrolytic enzymes, endo-arabinanase and α-L-arabinofuranosidase. In this study, the characterization and application in arabinan degradation of an endo-arabinanase from Thermotoga thermarum were investigated.ResultsThe recombinant endo-arabinanase was expressed in Escherichia coli BL21 (DE3) and purified by heat treatment followed by purification on a nickel affinity column chromatography. The purified endo-arabinanase exhibited optimal activity at pH 6.5 and 75°C and its residual activity retained more than 80% of its initial activity after being incubated at 80°C for 2 h. The results showed that the endo-arabinanase was very effective for arabinan degradation at higher temperature. When linear arabinan was used as the substrate, the apparent Km and Vmax values were determined to be 12.3 ± 0.15 mg ml−1 and 1,052.1 ± 12.7 μmol ml−1 min−1, respectively (at pH 6.5, 75°C), and the calculated kcat value was 349.3 ± 4.2 s−1.ConclusionsThis work provides a useful endo-arabinanase with high thermostability andcatalytic efficiency, and these characteristics exhibit a great potential for enzymatic conversion of arabinan.
Highlights
Arabinan is an important plant polysaccharide degraded mainly by two hydrolytic enzymes, endo-arabinanase and α-L-arabinofuranosidase
Amino acid sequence of Tth Abn The Tth abn gene isolated from the T. thermarum genome is 1,437 bp in length coding for 479 amino acids
The provisional β-xylosidase was confirmed as an endo-arabinanase through the biochemical analysis
Summary
Arabinan is an important plant polysaccharide degraded mainly by two hydrolytic enzymes, endo-arabinanase and α-L-arabinofuranosidase. The characterization and application in arabinan degradation of an endo-arabinanase from Thermotoga thermarum were investigated. A polysaccharide constituent of hemicellulose, is composed of α-1,2- and/or α-1,3-linked to a α-1,5-linked L-arabinofuranosyl backbone residues [3,4,5]. Arabinan mainly consists of L-arabinose residues, existing in rhamnogalacturonan regions of pectins in the cell walls of several plants [6]. Microbial enzymes including hydrolases have represented an important part in industry due to their various favorable properties [7]. To generate Larabinose from arabinan, two major hydrolytic enzymes, endo-arabinanase and α-L-arabinofuranosidase, are essential to the synergetic action. Endo-arabinanase (EC 3.2.1.99) can hydrolyze the arabinan α-1,5-linked L-arabinofuranosyl
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