AP endonucleases

Apurinic / apyrimidinic (AP) endonuclease (BRENDA = 4.2.99.18) is an enzyme involved in base excision repair pathway of DNA into (BER). Its main role in the repair of nucleotide mismatched or damaged DNA, is to create a nickname for a phosphodiester backbone of the AP site that was created when you delete a base DNA glycosylase is damaged. There are four types of endonuclease AP, which are classified according to their site of the incision. Class II AP and class I endonuclease sites unfounded 3 ‘and 5′ phosphate groups of DNA incision leaving the 5′-terminal phosphate and 3’-OH. Grade IV AP and grade III, endonuclease is a phosphate group to cut the DNA of the 3 ‘and 5′, they, 5′-OH and 3’-phosphate also generated site unfounded. In class Ⅱ, in order to play its role in base excision repair, (APE1), AP endonuclease most human AP endonuclease, require Mg2 in the active site. Yeast homolog of this enzyme is APN1.

AP endonuclease

It, AP to be able to respond selectively to objects, APE1, contains the amino acid residues of some. Positive residues Spread the minor groove and (Lys78 and Arg73, Ala74) residues and phosphate of DNA three consecutive coast to include an AP site while Gly127 span and three APE1 Tyr128, was found in four lines phosphate group of negative present in the phosphodiester backbone of the DNA and mounting of extreme refractive DNA caused by the interaction between the α-helix.

Work unfounded this extreme destructive power of DNA into the active site of APE1. Leu282 and Phe266, Trp280, this active site are adjacent to each other are packed tightly in the hydrophobic part of discrimination against sites that have site AP, based. The AP sites its partners orphan base is stabilized by hydrogen bonds with Met270, then, Asn174, Asn212, His309, and are stabilized by hydrogen bonds with phosphate groups of 5 to AP sites and ions Mg 2 . It is stabilized by hydrogen bonding phosphate groups AP sites, and 3 ‘Arg177. On the other hand, the maximum pH was observed in 7.5 APE1 probably the phosphodiester backbone to cut and attack caused by a stabilization in the active site that is made more reactive increase in (log acid dissociation constant or negative) pKa of course to Asp210 by hydrogen bond activation of nucleophilic Asn212 between Asn68 that is due to activities.

APE1 enzyme creates a participant phosphodiester backbone (unfounded) abasic site through Ashirushifuto of a simple mechanism. First, Asp210 residue in the active site, deprotonated molecules of water can make a nucleophilic attack on the phosphate group is located in the 5 ‘site AP. Then, the electrons are stabilized from one of the oxygen atoms of a phosphate group, both kicking oxygen with each other to create a free 5 ‘phosphate group without 3’-OH of the normal nucleotide and AP sites Mg2 ion for moving downward.

Inhibitor known APE1 7 – contains the lucanthone carboxylic acid (CA) – -2 nitro-indole. I have a ring associated with the short-circuit appears as phosphate bond in the DNA and deoxyribose sugar ring without basic application of both the structure of these. Both of these, H-bond acceptor many may be reacted These inhibitors are attached to the active site, thereby blocking the action of enzymes that catalyze other reactions, and H bond donor in the active center of APE1 I contains the body.

It therefore plays an important role in nucleotide excision repair pathway DNA, APE1 has become the subject of research for obtaining funds for preventing surviving cancer cells to chemotherapy. You can enzyme to recognize the AP-site involvement after road BER, it also, to have a redox function which helps to activate other enzymes, itself participated in the backbone of DNA APE1 need Involved in DNA repair as well as to create a user. As APE1 of subversion like this, and prevent cancer cells from the persistent after chemotherapy by it, can cause the sensitivity of tumor cells.