Endonuclease III from Escherichia coli is a DNA base excision repair enzyme that is involved in the recognition of an abnormal base followed by its removal (8).  DNA is in constant need of repair due to damage from alkylating and oxidative agents, radiation, spontaneous hydrolysis, and errors occurring during DNA replication (4).  Endonuclease III was originally identified as a DNA nicking activity seen after heavy ultraviolet radiation (10).  It is now known that endonuclease III is an enzyme that acts both as a DNA N-glycosylase, removing oxidized pyrimidines, and as an apurinic/apyrimidinic (AP) lyase, introducing a single stranded nick at the AP site from which the damaged base was removed (6).
            Endonuclease III is encoded by the nth gene and has been cloned, sequenced, over expressed, and purified in large quantities allowing the structure to be studied (1).  There are a conserved class of enzymes with the same specificity for damaged DNA found in bacteria, yeast, bovine cells, and human cells.  By studying endonuclease III it could have a wide range of implications in understanding DNA repair, and potentially, carcinogenisis and aging in higher organisms (6).

Table of Contents
Function 

[Structure][Active Site][DNA Interactions][References]