The International Enzyme Enginnering Symposium, Aydın, Turkey, vol.1, pp.64
Many types of amylases with unique p'roperties have been isolated and characterized for various applications in the starch industry. Amylases can be divided into several groups according to substrate specifities, patterns of starch cleavage, transglycosylation or cyclization activities and structural features . Maltogenic amylase (MAase; Glucan 1,4-alpha-maltohydrolase EC 188.8.131.52) is an amylase-type enzyme in glycoside hydrolase family 13. This type of enzyme is distinquishable from typical u-amylase by its extensive transglycosylation activity in addition to its hydrolysis activitiy. Maltogenic amylases, which are not secreted outside the cell, prefer cyclodextrins to starch or pullulan as a substrate .
In this study, the Cıoned and sequenced maltogenic amylase gene from the thermophilic bacterium, G. caldoxylolyticus TK4 was overexpressed under T7 promoter control in E. coli and the recombinant enzyme was purified by one-step nickel affinity chromatography. After staining by iodine solution, a clear-zone was observed in native electrophoresis gel including 1% starch. The enzyme preferred b-cyclodextrine (b-CD) to starch and degrade it mainly to maltose and glucose. So, characterization of the enzyme was performed by using 1% b-CD as a substrate. The optimum pH and temperature values were determined as 7.0 and 50 °C, respectively. When the enzyme incubated in buffer solutions ranging from pH 3.0-10.0 for 7 days at 50 °C, almost 100% of the activity was conserved. The activity was declined only 30% after 7 'days incubation at the optimum temperature.
The effects of metal ions and some chemicals on the activity were also investigated.