1996年 Mum menbrauer等发现野生型 P5 3蛋白具有内在的依赖 Mg2 + 的 3′- 5′核酸外切酶活性。本研究对一种缺陷型 P5 3蛋白 P5 3Δ 37是否具有这种核酸外切酶活性进行初步研究。结果发现 :P5 3Δ 37蛋白同样具有 3′- 5′核酸外切酶活性 ,并随着蛋白量的增加而增加 ,但一磷酸鸟嘌呤对该外切酶活性没有抑制作用。哺乳动物细胞内有许多过程涉及到核酸外切酶功能 ,如 DNA复制、DNA重组及 DNA修复 ,因此 ,这一功能在 DNA复制、重组和修复过程中具有重要的意义 In 1996, Mum menbrauer et al. Found that the wild-type P5 3 protein has intrinsic Mg2 + dependent 3’-5 ’exonuclease activity. This study conducted a preliminary study on whether or not a defective P5 3 protein P5 3Δ37 has this exonuclease activity. The results showed that the P5 3Δ37 protein also had 3’-5 ’exonuclease activity and increased with the increase of the amount of protein, but guanosine monophosphate did not inhibit the exonuclease activity. There are many processes within mammalian cells that involve exonuclease functions such as DNA replication, DNA recombination and DNA repair, so this function is of great importance in DNA replication, recombination and repair