Nes I F
Nucleic Acids Res. 1980 Apr 11;8(7):1575-89. doi: 10.1093/nar/8.7.1575.
An endonuclease specific for apurinic sites in double stranded DNA has been purified 373-fold from the nuclei of mouse plasmacytoma cells (line MPC-11). The enzyme is free of any detectable amounts of aspecific nucleases. The enzyme does not act on methylated or OsO4-treated DNA. However, high doses of UV-light and gamma-rays render the DNA slightly susceptible to endonucleolytic attack, which is believed to be due to depurination of depyrimidination caused by the treatment. The molecular weight of the enzyme is determined to be 28,000 and its apparent Km of the purified enzyme is calculated to be 2.7 nM apurinic sites. The activity is not absolutely dependent upon the presence of Mg2+ in the assay mixture although metal chelating agents such as sodium citrate and EDTA abolish the activity completely. The nuclease was stimulated by moderate concentrations of potassium chloride optimizing at 50 mM, and higher concentrations inhibiting the activity. The pH optimun for the reaction was 9.5.
一种特异性作用于双链DNA中脱嘌呤位点的核酸内切酶已从小鼠浆细胞瘤细胞（MPC - 11系）的细胞核中纯化出来，纯化倍数达373倍。该酶不含任何可检测到的非特异性核酸酶。该酶不作用于甲基化或经四氧化锇处理的DNA。然而，高剂量的紫外线和γ射线会使DNA对核酸内切酶的攻击稍有敏感性，据信这是由于处理导致的脱嘌呤或脱嘧啶作用。该酶的分子量测定为28,000，纯化酶的表观Km值经计算为2.7 nM脱嘌呤位点。尽管测定混合物中金属螯合剂如柠檬酸钠和EDTA会完全消除活性，但该酶的活性并非绝对依赖于Mg2+的存在。该核酸酶受到中等浓度氯化钾的刺激，在50 mM时活性最佳，更高浓度则抑制活性。该反应的最适pH为9.5。
