The soybean β-amylase [α-1, 4-glucan maltohydrolase, EC. 3. 2. 1. 2] is composed of seven isozymes( Ⅰ´, Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ), and isozyme Ⅱ and Ⅳ are the main components among these.
The purification of β-amylase isozymes from soybean whey were performed by ammonium sulfate fractionation, CM-Sephadex C-50 column chromatography, DEAE-Sephadex chromatography and Gel filtration. The resulted purity of β-amylase was throughly confirmed by electrophoresis, and then determined its isoelectric point and molecular weight. The results obtained were as follows ;
1. Five active fractions of soybean β-amylase were derived on CM-Sephadex C-50 column chromatography .
2. Seven active bands of β-amylase isozymes were detected by isoelectric focusing gel electrophoresis, and their isoelectric points ( Ⅰ´ to Ⅵ) were 5.07, 5.15, 5.25, 5.40, 5.55, 5.70 and 5.93, respectively.
3. Isozyme Ⅱ and Ⅳ were main components of soybean β-amylase.
4. The molecular weights of both isozyme Ⅱ and Ⅳ were determined to be 56,000 daltons by the result of SDS polyacrylamide gel electrophoresis.
5. Km values of main isozyme Ⅱ & Ⅳ for amylopectin were determined to be 2.25㎎/㎖, which suggest the same function of each isozyme.
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