title: Human placental apurinic/apyrimidinic endonuclease. Mechanism of action.
abstract: The mechanism of action of the homogeneous preparation of human placental apurinic/apyrimidinic (AP) endonuclease, described in the previous paper (Shaper, N. L., Grafstrom, R. H., and Grossman, L. (1982) J. Biol. Chem. 257, 13455-13458), has been investigated in detail. This enzyme cleaves apyrimidinic DNA both 5' and 3' to the site of damage in a ratio of 60:40, respectively. Even though this enzyme can cleave on both sides of an internal AP site, it does not release deoxyribose 5-phosphate from terminal AP sites. However, a compound, tentatively identified as alpha, beta unsaturated deoxyribose 5-phosphate, is nonenzymatically released only from 5'-terminal AP sites, presumably by a beta-elimination mechanism.
mesh_terms: D045647:DNA Glycosylases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D009699:N-Glycosyl Hydrolases; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013379:Substrate Specificity; D051981:Uracil-DNA Glycosidase
chemical_list: D004706:Endodeoxyribonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase