Purification and Characterization of a Novel β-Agarase from an Alkalophilic Bacterium, Alteromonas sp.E-1

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A novel β-agarase(EC 3.2.1.81)was purified from an agar-degrading alkalophilic bacterium, Alteromonas sp. E-1 isolated from the soil. This enzyme was obtained from a cell-free extract after sonication and purified 40.9-fold through treatment with streptomycin, ammonium sulfate fractionation and successive chromatography on anion-exchange and gel filtration columns. The molecular weight was estimated to be 82 kDa by SDS-polyacrylamide gel electrophoresis and 180 kDa by Superdex 200 gel filtration. The enzyme was inhibited by Mn^<2+>Cu^<2+>Fe^<2+>Zn^<2+> and Hg^<2+> and activated by K^+, Na^+ and EDTA, and its optimum pH and temperature for agarose degradation were 7.5 and 40°C, respectively. This β-agarase hydrolyzed agarose with rapid reduction of viscosity, and neoagarobiose [O-3, 6-anhydro-α-L-galactopyranosyl(1・3)-D-galactose]was detected from the early stage of the reaction. Neoagarobiose as the final product was selectively released from agarose, neoagarohexaose and neoagarotetraose by the reaction with this β-agarase. This observation was different from that of other β-agarases which produced mixtures of neoagarobiose and neoagarotetraose as the final hydrolysis products. The N-terminal amino acid sequence of this β-agarase shows no homology to those of other β-agarases that were so far reported.
社団法人日本生物工学会の論文
1999-04-25