サイクロデキストリン合成酵素の可溶性澱粉に対するエンド型作用の確認 Further Evidence for the Random Attack of Cyclodextrin Glucanotransferase on Soluble Starch

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Abstract

サイクロデキストりン合成酵素(CGTase)は基質の澱粉の非還元末端に作用してサイクロデキストリンを合成し,この事実から,CGTaseはエキソ型酵素に分類されている.最近になって,CGTaseが澱粉分子の内部に作用することが報告されている.可溶性澱粉および蛍光標識を行った可溶性澱粉に対するCGTaseの作用パターンをタカアミラーゼA(エンド型)およびグルコアミラーゼ(エキソ型)の作用パターンと比較してみると,CGTaseはエキソ型よりエンド型酵素に類似した作用特性を示すことがわかった.ヨウ素呈色の著しい低下にもかかわらず,還元糖の生成が極めて少ないことも,CGTase反応のもう一つの特徴として確認された.以上の結果から,CGTaseは基質の澱粉に対して,従来,知られているような非還元末端側からのエキソ型の作用のみならず,分子の内部を開裂するエンド型酵素に類似した作用を示す結果が得られた.

Cyclodextrin glucanotransferase (CGTase) produced cyclodextrin from the nonreducing terminals of substrate starch molecule, and this would provide a clue for the classification of CGTase into an exotype of enzyme. However, random cyclization reaction was recently demonstrated by an analysis of the initial action of CGTase. Further evidence for the random attack of CGTase on soluble starch was obtained by the following experiments. In a comparison of the cleavage pattern of CGTase on the fluorescent-labeled soluble starch with Taka-amylase A (endo-type) and glucoamylase (exo-type), the characteristics of CGTase were much closer to an endo-type action than to an exo-type action; namely, a rapid decrease in the substrate molecular weight was observed. A very low production of reducing sugar, in spite of a large decrease in blue value, was another characteristic obtained for the CGTase reaction, which would suggest that the production of oligomer fragments having a reducing end group was much less than that of cyclized fragments. These results show that CGTase attacked the starch substrate not only at sites close to the nonreducing terminals in an exo-type of cleavage, but also at sites in the middle of the substrate molecule in cleavage much like an endo-type.

Journal

  • Journal of Applied Glycoscience

    Journal of Applied Glycoscience 45(4), 373-378, 1998-12-01

    The Japanese Society of Applied Glycoscience

References:  15

Codes

  • NII Article ID (NAID)
    10008258382
  • NII NACSIS-CAT ID (NCID)
    AN10453916
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    13403494
  • NDL Article ID
    4635655
  • NDL Source Classification
    ZP24(科学技術--化学・化学工業--糖・澱粉)
  • NDL Call No.
    Z17-15
  • Data Source
    CJP  NDL  J-STAGE  JASI 
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