Mung Bean Nuclease I在来DNAの末期の加水分解

DNAの二重構造を支持する条件下では、Mung Bean Nucleaseは、ネイティブT7 DNAの内部に限られた数の二本鎖切断（おそらく50未満）を触媒します。ただし、緊密ならせん構造にそれほど好ましくない条件下では、以前に生成された大きな二重ポリマーは、モノ、ジ - 、トリヌクレオチドの連続的な蓄積で末端から完全に分解されます。末端に向けられた活性は、（1）単一鎖活性と並行して不活性化および再活性化されるため、（2）分析ゲル上の2つの活性が協力的であるためです。速度論的測定は、在来DNAの末端に向けられた加水分解の見かけのkmが比較的高いことを示しています。変性DNAの加水分解と、在来DNAの末端に向けられた加水分解の両方に最適なpHは、塩濃度の増加とともにより酸性になります。一本鎖構造の相対的な好みは、pHがより基本的になるにつれて増加します。

Under conditions which favor the duplex structure of DNA, mung bean nuclease catalyzes a limited number of double-strand cleavages (probably less than 50) in the interior of native T7 DNA. However, under conditions which are not as favorable to a tight helical structure, the large duplex polymers previously produced are completely degraded from their termini with a continuous accumulation of mono-, di-, and trinucleotides. The terminally directed activity is an intrinsic property of the enzyme molecule because (1) it is inactivated and reactivated in parallel with the single-strand activity and (2) the two activities coelectrophorese on analytical gels. Kinetic measurements indicate that the apparent Km for the terminally directed hydrolysis of native DNA is relatively high. The pH optimum for both the hydrolysis of denatured DNA and the terminally directed hydrolysis of native DNA becomes more acidic with increasing salt concentration. The relative preference for single-stranded structures increases as the pH becomes more basic.