Arabinoxylo- and Arabino-Oligosaccharides- Specific α-L-Arabinofuranosidase GH51 Isozymes from the Amylolytic Yeast Saccharomycopsis fibuligera = Arabinoxylo- and Arabino-Oligosaccharides- Specific α-L-Arabinofuranosidase GH51 Isozymes from the Amylolytic Yeast Saccharomycopsis fibuligera

다국어 초록 (Multilingual Abstract)

Two genes encoding probable α-L-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 40~45oC and pH 7.0 in sodium phosphate buffer and at 50oC and pH 6.0 in sodium acetate buffer, respectively. These exoacting enzymes belonging to the glycoside hydrolase (GH) family 51 could hydrolyze arabinoxylooligosaccharides (AXOS) and arabino-oligosaccharides (AOS) to produce only L-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)-L-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.