Molecular Characterization of a Novel 1,3-α-3,6-Anhydro-L-Galactosidase, Ahg943, with Cold- and High-Salt-Tolerance from Gayadomonas joobiniege G7
서주원, Tsevelkhorloo Maral, 이창로, 김상훈, 강대경, Asghar Sajida, 홍순광,
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서주원 ( Seo Ju-Won ) - Myongji University Department of Bioscience and Bioinformatics
( Tsevelkhorloo Maral ) - Myongji University Department of Bioscience and Bioinformatics
이창로 ( Lee Chang-Ro ) - Myongji University Department of Bioscience and Bioinformatics
김상훈 ( Kim Sang-Hoon ) - Dankook University Department of Animal Resources Science
강대경 ( Kang Dae-Kyung ) - Dankook University Department of Animal Resources Science
( Asghar Sajida ) - Myongji University Department of Bioscience and Bioinformatics
홍순광 ( Hong Soon-Kwang ) - Myongji University Department of Bioscience and Bioinformatics
Abstract
1,3-α-3,6-anhydro-L-galactosidase (α-neoagarooligosaccharide hydrolase) catalyzes the last step of agar degradation by hydrolyzing neoagarobiose into monomers, D-galactose, and 3,6-anhydro-Lgalactose, which is important for the bioindustrial application of algal biomass. Ahg943, from the agarolytic marine bacterium Gayadomonas joobiniege G7, is composed of 423 amino acids (47.96 kDa), including a 22-amino acid signal peptide. It was found to have 67% identity with the α-neoagarooligosaccharide hydrolase ZgAhgA, from Zobellia galactanivorans, but low identity (< 40%) with the other α-neoagarooligosaccharide hydrolases reported. The recombinant Ahg943 (rAhg943, 47.89 kDa), purified from Escherichia coli, was estimated to be a monomer upon gel filtration chromatography, making it quite distinct from other α-neoagarooligosaccharide hydrolases. The rAhg943 hydrolyzed neoagarobiose, neoagarotetraose, and neoagarohexaose into D-galactose, neoagarotriose, and neoagaropentaose, respectively, with a common product, 3,6- anhydro-L-galactose, indicating that it is an exo-acting α-neoagarooligosaccharide hydrolase that releases 3,6-anhydro-L-galactose by hydrolyzing α-1,3 glycosidic bonds from the nonreducing ends of neoagarooligosaccharides. The optimum pH and temperature of Ahg943 activity were 6.0 and 20°C, respectively. In particular, rAhg943 could maintain enzyme activity at 10°C (71% of the maximum). Complete inhibition of rAhg943 activity by 0.5 mM EDTA was restored and even, remarkably, enhanced by Ca2+ ions. rAhg943 activity was at maximum at 0.5 M NaCl and maintained above 73% of the maximum at 3M NaCl. Km and Vmax of rAhg943 toward neoagarobiose were 9.7 mg/ml and 250 μM/min (3 U/mg), respectively. Therefore, Ahg943 is a unique α-neoagarooligosaccharide hydrolase that has cold- and high-salt-adapted features, and possibly exists as a monomer.
키워드
1,3-α-3,6-anhydro-L-galactosidase; α-neoagarooligosaccharide hydrolase; Gayadomonas joobiniege G7; cold- and salt-tolerant; monomer
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