Abstract
Amylases of kiwifruit were purified by ammonium sulfate precipitation, followed by Affinity chromatography (a-cyclodextrin sepharose 6B) and chromatofocusing (polyexchanger PBE94). Two different amylases were obtained in pure state and tentatively designated as Amylase I and II. Amylase I and II were found to be a single band when examined by electrophoresis. The specific activity of Amylase I and II was 1, 517 and 372-fold of the crude extract enzyme, respectively. Amylase I and II had molecular weights of 43, 000 and 40, 000; and showed the highest activity at pH 7.0, 55°C, respectively. Amylase I and II were stable at pH 6.0-8.0 and below 50°C. The Km values for soluble starch of Amylase I and II were calculated to be 9.5 and 17.9 mg/ml, respectively. Both activities of the enzymes were inhibited by Hg2+. Qualitative thin-layer chromatographic analysis on the starch solution digested two enzymes revealed specificity of products. Amylase I produced a maltopentaose at first and later produced maltotetraose, maltotriose and maltose, while Amylase II produced maltotetraose, maltotriose and maltose from soluble starch.
