Purification and Characterization of Limit Dextrinase from Malted Barley

摘要

Limit dextrinase is one of three main amylases in malted barley, which plays a significant role during the mashing stage of brewing. Due to very low content and similar properties compared to other amylases in malted barley, limit dextrinase is hard to separate effectively. Our work had been directed towards the extraction and purification of limit dextrinase from malted barley. Final products were obtained through fraction precipitation with ammonium sulfate and column chromatography, and purified limit dextrinase acquired a high purity of 31.23 times as much as that of crude extracts. The previous results were also confirmed by sodiumdodecyl sulphate poly-acrylamide gel electrophoresis (SDS-PAGE) revealing a single band of protein (～97KDa). Effect of temperature, pH value, and metal ion on hydrolysis characterization of limit dextrinase was investigated. The results indicated that the maximum activity of purified samples changed significantly compared with that of crude extracts. The activity of purified limit dextrinase could be activated by lower concentration of Mg~(2+), Ca~(2+), MN~(2+) and inhibited by the action of ZN~(2+), Fe~(2+). But this influence was not so obvious for K~+.