César R, Verly W G
Eur J Biochem. 1983 Jan 1;129(3):509-17. doi: 10.1111/j.1432-1033.1983.tb07077.x.
The extract from rat liver chromatin contains two apurinic/apyrimidinic (AP) endodeoxyribonucleases named 0.2 M and 0.3 M isozymes according to the phosphate concentration necessary to elute them from an hydroxyapatite column. The 0.3 M isozyme is the main and perhaps the only chromatin AP endodeoxyribonuclease in the living cell. This 0.3 M isozyme was purified by successive chromatographies on hydroxyapatite, phosphocellulose, heparin-Sepharose and alkylated-depurinated DNA-cellulose. It has a molecular weight of approximately 39000; its optimum pH is around 8.0; it needs Mg2+ or Mn2+ to be active and the optimum concentration for Mg2+ is between 5 mM and 10 mM. The 0.3 M isozyme has no action on intact DNA strands or on alkylated sites; it cuts the phosphodiester bridge which is the immediate neighbour of the AP site on its 5' side leaving 3'-hydroxyl and 5'-phosphate ends. It has no associated exonuclease activity. To hydrolyze the phosphoester bond near the AP site, the enzyme makes a close contact with three base residues in the large groove of the DNA molecule.
大鼠肝脏染色质提取物含有两种无嘌呤/无嘧啶（AP）内切脱氧核糖核酸酶，根据从羟基磷灰石柱上洗脱它们所需的磷酸盐浓度，分别命名为0.2M和0.3M同工酶。0.3M同工酶是活细胞中主要的，也许是唯一的染色质AP内切脱氧核糖核酸酶。这种0.3M同工酶通过在羟基磷灰石、磷酸纤维素、肝素-琼脂糖和烷基化-脱嘌呤DNA-纤维素上连续色谱法进行纯化。它的分子量约为39000；其最适pH值约为8.0；它需要Mg2+或Mn2+才有活性，Mg2+的最适浓度在5mM至10mM之间。0.3M同工酶对完整的DNA链或烷基化位点没有作用；它切割磷酸二酯桥，该桥在其5'侧与AP位点直接相邻，留下3'-羟基和5'-磷酸末端。它没有相关的外切核酸酶活性。为了水解AP位点附近的磷酸酯键,该酶与DNA分子大沟中的三个碱基残基紧密接触。
