title: Novel acidophilic β-galactosidase with high activity at extremely acidic pH region from Teratosphaeria acidotherma AIU BGA-1.
abstract: A β-galactosidase exhibiting maximal activity at pH 1.0 was purified from Teratosphaeria acidotherma AIU BGA-1. The enzyme had a molecular mass of 180 kDa and consisted of two heterosubunits of 120 kDa and 66 kDa. The N-terminal amino acid sequence of the large subunit was found to be SPNLQDIVTVDGESY. These physicochemical properties differed from those of other microbial β-galactosidases. At pH values of 1.5 and pH 4.5, the enzyme exhibited its highest activity at temperatures of 70°C and 80°C, respectively. Thus, the enzyme exhibited the lowest optimal pH and highest optimal temperature among the microbial β-galactosidases thus reported. The enzyme retained more than 80% of its original activity in the pH range from 2.0 to 8.0 by incubation at 50°C for 30 min. The enzyme hydrolyzed 4-nitrophenyl-β-D-fucopyranoside, 2-nitrophenyl-β-D-galactopyranoside, and 4-nitrophenyl-β-D-galacto-pyranoside at relative reaction rates of 100, 59, and 24, respectively, at pH 1.5, and its affinity for β-D-galactopyranosides was higher than that for β-D-fucopyranosides. The enzyme also efficiently hydrolyzed lactose in milk and whey from yoghurt at pH 1.5.
authors: Department of Biological Chemistry and Food Science, Iwate University, 18-8 Ueda-3, Morioka 020-8550, Japan.
authors: Serina
authors: S
authors: Chiba
authors: Department of Biological Chemistry and Food Science, Iwate University, 18-8 Ueda-3, Morioka 020-8550, Japan.
authors: Miwa
authors: M
authors: Yamada
authors: Department of Biological Chemistry and Food Science, Iwate University, 18-8 Ueda-3, Morioka 020-8550, Japan. Electronic address: kiso@iwate-u.ac.jp.
authors: Kimiyasu
authors: K
authors: Isobe
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000201:enzymology*; D005643:Fucose / Q000031:analogs & derivatives; D005690:Galactose / Q000031:analogs & derivatives / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D043322:Lactase / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D021122:Protein Subunits / Q000737:chemistry; D013379:Substrate Specificity; D013696:Temperature; D000067796:Whey / Q000378:metabolism; D001616:beta-Galactosidase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D005643:Fucose; D043322:Lactase; D001616:beta-Galactosidase; D007785:Lactose; D005690:Galactose
keywords: Acidophilic lactase; Lactase; Lactose; Teratosphaeria acidotherma; β-Galactosidase