Abstract
The β-galactosidase exhibiting high activity from an extremely acidic pH region to neutral pH region was efficiently purified from an acidophilic fungus, Teratosphaeria acidotherma AIU BGA-1, using affinity chromatography with Toyopearl resins immobilized 4-aminophenyl-β-d-galactopyranoside. The enzyme was stable in the pH range from 1.5 to 7.0, and exhibited optimal activity at pH 2.5-4.0 and 70°C. 2-Nitrophenyl-β-d-galactopyranoside, 4-nitrophenyl-β-d-galactopyranoside and lactose were rapidly hydrolyzed, and the apparent Km values were estimated to be 0.19mM, 1.2mM and 170mM, respectively. Thus, the enzyme can be used in the wide pH range for hydrolysis of lactose. The molecular mass of the enzyme was estimated to be 140kDa with two hetero subunits of 86kDa and 50kDa. The N-terminal amino acid sequence of the small subunit was found to be NTRMIIFNDK. These enzymatic and physicochemical characteristics are remarkably different from those of the previously known β-galactosidases.
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