Characterization of Exo-dextranase from Aspergillus ustus

Aspergillus ustus의 Exo-dextranase의 특성에 관한 연구

Exodextranase from Aspergillus ustus was purified by chromatography and characterized by various conditions. The optimal pH of the purified dextranase was 6.5 and this enzyme was maximally activated at $40^{\circ}C$. The enzyme was stable at the temperature below $50^{\circ}C$. The enzyme was markedly inactivated by $Hg^{2+},\;Cu^{2+},\;KCN\;and\;Co^{2+},\;but\;Ba^{2+},\;Fe^{2+},$ cysteine, EDTA, and ascorbic acid enhanced the activity of the enzyme. The main products from the hydrolysis of dextran incubated with the dextranase were glucose, isomaltotriose and oligosaccharide. When dextran was incubated with the mixture of pullulanase and ${\alpha}-amylase$, it was hydrolyzed into glucose, isomaltose and oligosaccharide. Polysaccharides in the decade teeth powder were hydrolyzed by the dextranase into glucose, isomaltotriose and oligosaccharides. In the hydrolysis of the teeth powder with the mixture of dextranase, pullulanase and ${\alpha}-amylase$, were proved to be similar to the dextran hydrolysates.

정제된 Aspergillus ustus의 dextranase 특성을 조사하기 위하여 최적 pH 최적온도 및 열 안정성 금속이온의 영향 및 분해산물을 조사하였다. 기질로는 dextran을 사용했다. 조사결과 dextranase의 활성 최적 pH는 6.5였으며, 작용 최적온도는 $40^{\circ}C$이고, $30^{\circ}C{\sim}35^{\circ}C$에서 비교적 분해능이 좋았고, 열 안전성은 $50^{\circ}C$에서 1시간 처리한 경우 약 91%의 잔존역가를 나타내고, $70^{\circ}C$에서는 약 38%의 잔존역가를 나타내 $50^{\circ}C$까지는 안정한 것으로 나타났다. 금속이온 등의 영향은 cysteine, ascorbic acid와 EDTA에서 상승작용을 나타내고, $Cu^{2+},\;KCN,\;Co^{2+}$에서는 약한 저해 작용을 나타내고, $Hg^{2+}는 완전히 저해되었다. 덱스트란을 분해시킨 분해산물은 glucose와 isomaltotriose및 그 이상의 분자량을 가지는 oligosaccharide로 구성되어 있고, 치아부착 다당류에 대한 분해도 덱스트란과 유사하였다.