Abstract
An active β-amylase was purified from germinated rice seeds by precipitation with ammonium sulfate, acid treatment, chromatographies on DEAE-cellulose and DEAE-Sephadex A-50, and gel filtrations on Sephadex G-75. The purified enzyme was homogeneous in disc electrophoretic analysis.
The molecular weight was estimated to be approximately 53, 000 by thin-layer gel filtration and polyacrylamide gel electrophoresis. The isoelectric point was found to be pH 5.0 by disc electrofocusing.
The optimum pH was found to be in the pH range of 5.5 to 6.5. The Km value for soluble starch was 3mg/ml. The enzyme was inhibited by sulfhydryl reagents or heavy metal ions.
The active β-amylase was oxidatively dimerized by treatment with 0.3M ferricyanide in 3M urea. The dimerized enzyme was thought to be one of inert β-amylases in ungerminated rice seeds.
