Sandigursky M, Franklin W A
Department of Radiology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Radiat Res. 1998 Dec;150(6):609-11.
The bacteria Escherichia coli contains several exonucleases acting on both double- and single-stranded DNA, and in both a 5'--> 3' and a 3' --> 5' direction. These enzymes are involved in replicative, repair and recombination functions. A new exonuclease recently identified in E. coli, termed exonuclease IX, acts preferentially on single-stranded DNA as a 3'--> 5' exonuclease and also functions as a 3' phosphodiesterase on DNA containing 3' incised apurinic/apyrimidinic (AP) sites to remove the product trans-4-hydroxy-2-pentenal-5-phosphate. We now demonstrate that the enzyme is also able to remove 3' phosphoglycolate end groups from DNA. This activity may have an important role in DNA base excision repair in E. coli.
大肠杆菌含有多种作用于双链和单链DNA的核酸外切酶，其作用方向既有5'→3'，也有3'→5'。这些酶参与复制、修复和重组功能。最近在大肠杆菌中鉴定出一种新的核酸外切酶，称为核酸外切酶IX，它优先作为3'→5'核酸外切酶作用于单链DNA，并且还作为3'磷酸二酯酶作用于含有3'切口的无嘌呤/无嘧啶（AP）位点的DNA，以去除反式-4-羟基-2-戊烯醛-5-磷酸产物。我们现在证明该酶还能够从DNA中去除3'磷酸乙醇酸末端基团。这种活性可能在大肠杆菌的DNA碱基切除修复中起重要作用。
