Purification and Characterization of Sea Squirt α-N-Acetylgalactosaminidase

概要

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Sea squirt α-N-acetylgalactosaminidase was purified to homogeneity. Its molecular weight was estimated to be approximately 160, 000 by gel filtration and 40, 000 by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing condition. The chromatographic and electrophoretic behaviors indicated that the enzyme was composed of four subunits. The optimum pH of the enzyme reaction was about 4.0 at 37℃, while the enzyme was stable in the range of pH 5.0 to 6.0 during 4 h preincubation at 37℃. Although the enzyme (0.1 unit) was stable at 0℃ for 30 min in the presence of 7.5 mM metal ions (Al^<3+> Ba^<2+> Ca^<2+> K^+, Mn^<2+> Pb^<2+> Sr^<2+> and Zn^<2+>), almost 40% of the enzyme activity was lost in the presence of Cu^<2+> Hg^<2+> monoiodoacetic acid, and EDTA. The enzyme hydrolyzed aryl N-acetyl-α-_D-galactosaminide as well as GalNAcα1(→4GalNAcα1→)_n 4GalNAc-p-aminobenzoic acid ethyl ester (ABEE) (n=1-4), but GalNAcα1→4GalNAc-ABEE only scarcely. Furthermore, an allergenic pentasaccharitol ABEE derivative, GalNAcα1→2Fucα1→3(GalNAcβ1→4) GlcNAcβ1→2(3-acetoamido-3-deoxy)_L-threose-ABEE, the minimum structural unit for the sea squirt allergenicity was hydrolyzed to 95 mol% for 72 h incubation with the enzyme. The enzyme could be utilized as a powerful tool for the structural analyses of the carbohydrate epitopes of the sea squirt allergen molecules.
社団法人日本生物工学会の論文
2000-01-25