호알칼리성 Bacillus sp.가 생산하는 Cyclodextrin Glycosyltransferase의 효소적 특성

Enzymatic Properties of Cyclodextrin Glycosyltransferase from Alkalophilic Bacillus sp. YC-335

호알칼리성 Bacillus sp. YC-335가 생산하는 CGTase의 효소학적 특성 및 작용반응을 살펴보았다. ${\alpha}-CD,\;{\beta}-CD$ 및 ${\gamma}-CD$로부터 glucosyl residues를 설탕으로 전이시키는 반응에 대한 효소의 최대 반응속도, Vmax 값은 각각 $16.13,\;21.8,\;9.8{\mu}moles glucose/min/mg\;protein$이었으며 Km 값은 각각 1.68, 0.33, 0.37 mM이었다. 효소의 전분 가수분해활성은 여러 당류에 의해 촉진되었으며 특히 전분 가수분해 산물인 maltose와 glucose에 의한 효과가 가장 좋았다. 이 효소는 ${\beta}CD$에 의해 효소의 전분 분해활성이 저해되었으며 비경쟁적 저해형식을 보였다. 또한 전분으로부터 효소작용에 의해 생성된 산물을 총당량법 및 HPLC 분석을 통해 조사한 결과 이 효소는 cyclization 작용 뿐만 아니라 transglycosylation 작용과 disproportionation 작용을 가지는 것으로 확인하였다.

The enzymatic properties of purified CGTase from alkalophilic Bacillus sp. YC-335 have been examined. Apparent Vmax values of the enzyme in transferring glycosyl residues ${\alpha}-,\;{\beta}-and\;{\gamma}-cyclodextrin(CD)$ to sucrose were $16.13,\;21.8\;and\;9.8{\mu}moles/min/mg\;protein$, respectively and Km values of the corresponding CD were 1.68, 0.33 and 0.37 mM, respectively. A number of saccharides, specially starch hydrolyzates such as glucose and maltose, could activate the dextrinizing activity of the enzym. However, the dextrinizing activity was inhibited by ${\beta}-CD$. It was found from Lineweaver-Burk plot that the inhibition of CGTase by ${\beta}-CD$ was noncompetitive. High performance liquid chromatographic analysis showed that the enzyme has three kinds of activity ; transglycosylation and disproportionation as well as cyclization.