NTH E.Coli

Endonuclease III plays a crucial role in the DNA repair mechanism. It possesses both DNA glycosylase and apurinic/apyrimidinic (AP) lyase activities . The DNA glycosylase activity of Endo III recognizes and removes damaged pyrimidines, such as thymine glycol, 5-hydroxycytosine, and 5,6-dihydro-thymine . This activity generates an AP site, which is then cleaved by the AP lyase activity via β-elimination, creating a 1-nucleotide gap with 3’-α, β-unsaturated aldehyde and 5’-phosphate termini .

The enzyme is encoded by the nth gene in E. coli . It is an iron-sulfur containing protein that protects E. coli cells from radiation damage caused by X-ray and UV irradiation . Additionally, when overexpressed, Endo III can protect E. coli cells from alkylation defects caused by methyl methanesulfonate .

Endonuclease III is supplied as a solution in 50% glycerol containing 20 mM Tris, pH 7.4, 100 mM NaCl, 1 mM EDTA, and 1 mM DTT . It is recommended to store the enzyme at 0 to -20 °C . The enzyme’s specific activity is defined as the amount of protein that cleaves 50% of 0.5 pmole of double-stranded oligonucleotide substrate containing 5,6-dihydrothymine (DHT) in 15 minutes at pH 7.6 at 30 °C .

Endonuclease III is widely used in molecular biology research, particularly in studies involving DNA repair mechanisms. Its ability to recognize and remove damaged bases makes it a valuable tool for understanding the cellular response to DNA damage and the repair processes that maintain genomic integrity .