Aprataxin is a DNA-binding protein involved in different types of DNA break repair. The enzyme acts (among other activities) on abortive DNA ligation intermediates that contain an adenylate covalently linked to the 5′-phosphate DNA terminus. It also acts when the adenylate is covalently linked to the 5′-phosphate of a ribonucleotide linked to a DNA strand, which is the result of abortive ligase activty on products of EC?3.1.26.4, ribonuclease H, an enzyme that cleaves RNA-DNA hybrids on the 5′ side of the ribonucleotide found in the 5′-RNA-DNA-3′ junction. Aprataxin binds the adenylate group to a histidine residue within the active site, followed by its hydrolysis from the nucleic acid and eventual release, leaving a 5′-phosphate terminus that can be efficiently rejoined. The enzyme also possesses the activities of EC?3.1.11.8, 5′-(5′-diphosphoguanosine)-DNA diphosphatase, and EC?3.1.12.2, DNA-3′-(5′-diphosphoguanosine) diphosphatase.
![Example Structure of adenosine-5'-diphospho-5'-[DNA] diphosphatase EC#: 3.1.11.7](/wp-content/uploads/enzyme-structure/3.1.11.7.jpg)