title: Purification and properties of two endonucleases specific for apurinic/apyrimidinic sites in DNA from Saccharomyces cerevisiae.
abstract: Two distinct endonucleases from Saccharomyces cerevisiae, specific for apurinic/apyrimidinic sites (AP-endonucleases A and B), have been extensively purified and characterized. Both are free from unspecific and ultraviolet-specific endonucleases and exonucleases. The two enzymes are monomeric proteins of around 24000 daltons. Both are sensitive to ionic strength and most active in the presence of 150 and 100 mM NaCl for AP-endonucleases A and B, respectively. They are not absolutely dependent on divalent cations, since they are insensitive to EDTA, although AP-endonuclease A is activated by Ca2+ or Mg2+ and AP-endonuclease B by Mg2+ only. ATP inhibits the enzymes. AP-endonuclease A reacts optimally between pH 6 and 8, and AP-endonucleases B at pH 8. AP-endonuclease A is more stable at 60 degree C (half-life of 17 min) than B (half-life of 4 min). AP-endonuclease A is insensitive to N-ethylmaleimide or rho-chloromercuribenzoate. AP-endonuclease B is also insensitive to N-ethylmaleimide, but rho-chloromercuribenzoate inhibits its activity.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004247:DNA; D004720:Endonucleases / Q000032:analysis / Q000302:isolation & purification*; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D000255:Adenosine Triphosphate; D004247:DNA; D004720:Endonucleases; D008274:Magnesium; D002118:Calcium