A Bio-engineering Study on a Transglucosylase, Dextrin Dextranase
2000
Masayuki Suzuki
Dextrin dextranase (DDase, 8C2.4.1.2) was extracellularly secreted in a culture medium of Acetobacter capsulatum ATCC 11894 containing both glucose (5.45Vo) and an extremely small amount of dextrin (0.05V0) as the essential carbon sources. The enzyme was simply purified by only one-step centrifugation at 4C and 20,00 0 X g for 2O min, and immediately dialyzed against 50 mM acetate buffer (pH a.5 ) at 4'C for 2-3 days. The purified DDase gave a single protein band on both Native-and SDS-PAGE. The physicochemical and enzymatic properties of the purified DDase were precisely investigated. The purified enzyme effectively synthesizad a -1, 6-glucan from maltooligosaccharides. The average molecular mass of the product dextran was estimated to be about I,270kDa.
The kinetic studies of the purified DDase were performed by using a series of maltooligosaccharides (DP :3-7) and a
short chain amylose (DP+ 17.3). The mode of inhibition of dextran formation by DDase action was a mixed type. From the inhibition studies of DDase, malthose molecules were definitely able to be glucosyl acceptors. Therefor, various oligosaccharides were able to be prepared from a high concentration of maltose as both glucosyl donors and acceptors. The oligosaccharides formed were separated, purified and analyzedby lH-and l3C- NMR.
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