Bifidobacterium bifidumの乳酸脱水素酵素

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書誌事項

タイトル別名
  • Lactate Dehydrogenase of Bifidobacterium bifidum
  • Bifidobacterium bifidum ノ ニュウサン ダッスイソ コウソ

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抄録

Bifidobacterium bifidum DSM20456からNAD^+依存性の乳酸脱水素酵素(LDH)を電気泳動的にほぼ均一な状態に精製した。この酵素はピルビン酸からの乳酸生成のみならず,乳酸からピルビン酸への酸化反応においても,その活性発現にフルクトース1,6-二リン酸を要求したが,それぞれの反応における酵素の基質に対する親和性は,ピルビン酸の方が乳酸よりも2,000倍近く高かった。

Lactate dehvdrogenases (LDHs) (EC 1.1.1.27) from some bacteria are allosteric enzymes with sigmoidal kinetics for pyruvate, unlike non-allosteric vertebrate LDHs 1)～7). Bifidobacterial LDHs are also allosterically activated by pyruvate (homotropic activation) and by fructose 1, 6-bisphosphate (FDP) (heterotropic activation) 8). These enzymes are virtually unidirectional, catalysing efficiency only the reduction of pyruvate and were extensively studied for their allosteric effectors. However, little is known about the oxidation reaction of lactate to pyruvate with NAD^+ (reversible reaction). In this work, we have demonstrated that FDP-activated NAD^+ -dependent LDH from Bifidobacterium bifidum DSM20456 was purified to homogeneity as judged by sodium dodecyl sulfate-gel electrophoresis. The purification consisted of ammonium sulfate precipitation of the cytoplasmic fraction, DE-32 chromatography, Sephacryl S-200 gel permeation, Affi-Gel Blue and Protein Pak G-DEAE chromatographies. Only when FDP existed, the oxidation reaction of the lactic acid with this purified enzyme took place as well as the case of the reduction reaction of the pyruvic acid. The pH optima of the activities and kinetic properties of the enzyme were studied. From these results, we conclude that LDH of Bifidobacterium bifidum DSM20456 was dependent on FDP for the reversible reactions but that apparent Km value of this enzyme for lactate was about 2,000 times as large as that for pyruvate.

11

KJ00005217789

研究ノート

収録刊行物

  • 學苑

    學苑 806 50-55, 2007-12-01

    東京 : 光葉会

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