• Journal of Microbiology and Biotechnology
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• 제29권1호
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• pp.37-43
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• 2019

The gene encoding an ${\alpha}-{\text\tiny{L}}-arabinofuranosidase$ (BvAF) GH51 from Bacillus velezensis FZB42 was cloned and expressed in Escherichia coli. The corresponding open reading frame consists of 1,491 nucleotides which encode 496 amino acids with the molecular mass of 56.9 kDa. BvAF showed the highest activity against sugar beet (branched) arabinan in 50 mM sodium acetate buffer (pH 6.0) at $45^{\circ}C$. However, it could hardly hydrolyze debranched arabinan and arabinoxylans. The time-course hydrolyses of branched arabinan and arabinooligosaccharides (AOS) revealed that BvAF is a unique exo-hydrolase producing exclusively ${\text\tiny{L}}-arabinose$. BvAF could cleave ${\alpha}-(1,2)-$ and/or ${\alpha}-(1,3)-{\text\tiny{L}}-arabinofuranosidic$ linkages of the branched substrates to produce the debranched forms of arabinan and AOS. Although the excessive amount of BvAF could liberate ${\text\tiny{L}}-arabinose$ from linear AOS, it was extremely lower than that on branched AOS. In conclusion, BvAF is the arabinan-specific exo-acting ${\alpha}-{\text\tiny{L}}-arabinofuranosidase$ possessing high debranching activity towards ${\alpha}-(1,2)-$ and/or ${\alpha}-(1,3)-linked$ branches of arabinan, which can facilitate the successive degradation of arabinan by $endo-{\alpha}-(1,5)-{\text\tiny{L}}-arabinanase$.

• Journal of Microbiology and Biotechnology
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• 제31권2호
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• pp.272-279
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• 2021

Two genes encoding probable α-ʟ-arabinofuranosidase (E.C. 3.2.1.55) isozymes (ABFs) with 92.3% amino acid sequence identity, ABF51A and ABF51B, were found from chromosomes 3 and 5 of Saccharomycopsis fibuligera KJJ81, an amylolytic yeast isolated from Korean wheat-based nuruk, respectively. Each open reading frame consists of 1,551 nucleotides and encodes a protein of 517 amino acids with the molecular mass of approximately 59 kDa. These isozymes share approximately 49% amino acid sequence identity with eukaryotic ABFs from filamentous fungi. The corresponding genes were cloned, functionally expressed, and purified from Escherichia coli. SfABF51A and SfABF51B showed the highest activities on p-nitrophenyl arabinofuranoside at 40~45℃ and pH 7.0 in sodium phosphate buffer and at 50℃ and pH 6.0 in sodium acetate buffer, respectively. These exoacting enzymes belonging to the glycoside hydrolase (GH) family 51 could hydrolyze arabinoxylo-oligosaccharides (AXOS) and arabino-oligosaccharides (AOS) to produce only ʟ-arabinose, whereas they could hardly degrade any polymeric substrates including arabinans and arabinoxylans. The detailed product analyses revealed that both SfABF51 isozymes can catalyze the versatile hydrolysis of α-(1,2)- and α-(1,3)-ʟ-arabinofuranosidic linkages of AXOS, and α-(1,2)-, α-(1,3)-, and α-(1,5)-linkages of linear and branched AOS. On the contrary, they have much lower activity against the α-(1,2)- and α-(1,3)-double-substituted substrates than the single-substituted ones. These hydrolases could potentially play important roles in the degradation and utilization of hemicellulosic biomass by S. fibuligera.