Brent T P
Biochemistry. 1983 Sep 13;22(19):4507-12. doi: 10.1021/bi00288a024.
An endonuclease activity for UV-irradiated DNA, gamma-irradiated DNA, and OsO4-treated DNA that was partially purified from human lymphoblasts was found to have associated with it an endonuclease activity for partially depurinated DNA. When this apurinic endonuclease (Endo A) was characterized and compared with the cells' major apurinic endonuclease (Endo B), several notable differences were observed. (1) Endo A bound to oxidized DNA-Sepharose under conditions where Endo B did not. (2) Endo A did not require Mg2+, retaining full activity in 10 mM ethylenediamine-tetraacetic acid, while Endo B showed an absolute requirement for Mg2+. (3) Whereas the nicks made in depurinated DNA by Endo B were efficient priming sites for Escherichia coli polymerase I, those made by Endo A were not. Further characterization of the nicks indicated that Endo A incises depurinated DNA 3' to apurinic sites, leaving 3'-terminal deoxyribose, a poor priming site for DNA synthesis. Endo A action on UV-irradiated DNA produced nicks that resembled those it made in depurinated DNA, suggesting that the UV endonuclease activity acts through an apurinic/apyrimidinic site intermediate.
从人淋巴母细胞中部分纯化得到的一种核酸内切酶活性，对紫外线照射的DNA、γ射线照射的DNA以及经四氧化锇处理的DNA具有活性，同时发现它还具有对部分脱嘌呤DNA的核酸内切酶活性。当对这种脱嘌呤核酸内切酶（内切酶A）进行特性鉴定并与细胞中的主要脱嘌呤核酸内切酶（内切酶B）进行比较时，观察到了几个显著差异。（1）在内切酶B不结合的条件下，内切酶A能与氧化型DNA-琼脂糖结合。（2）内切酶A不需要Mg2+，在10 mM乙二胺四乙酸中仍保持全部活性，而内切酶B则绝对需要Mg2+。（3）内切酶B在脱嘌呤DNA上产生的切口是大肠杆菌DNA聚合酶I的有效引物位点，而内切酶A产生的切口则不是。对这些切口的进一步特性分析表明，内切酶A在脱嘌呤位点的3'端切割脱嘌呤DNA，留下3'-末端脱氧核糖，这是DNA合成的不良引物位点。内切酶A对紫外线照射的DNA的作用产生的切口与它在脱嘌呤DNA上产生的切口相似，这表明紫外线核酸内切酶活性是通过脱嘌呤/脱嘧啶位点中间体起作用的。
