title: Deoxyribonucleic acid single-strand-specific endonucleases in human cells: partial purification of a salt-resistant endonuclease with an acidic isoelectric point.
abstract: A second endonuclease with DNA single-strand specificity has been purified from KB cells, a continuous line of hunan epithelial cells. In contrast to other mammalian enzymes that cleave single-stranded DNA, this enzyme has an acidic isoelectric point (6.5 +/- 0.2). Its pH optimum is 9.5, it requires Mg2+ of Mn2+ for activity, and it has a sedimentation coefficient of 3.2 S, based on sucrose gradient centrifugation. The enzyme specifically catalyzes the endonucleolytic cleavage of synthetic DNA homopolymers and denatured viral DNA but does not attack linear duplex viral DNA. The rate of hydrolysis of poly(dT) is approximately 8-fold greater than that observed with denatured DNA. The relative rates of hydrolysis of homopolymers by the endonuclease are poly(dA) greater than poly(dT) greater than poly(dC) greater than poly(dG). Unlike other DNA single-strand-specific endonucleases isolated from human cells, this endonuclease is relatively insensitive to inhibition by KCl.
mesh_terms: D002460:Cell Line; D004277:DNA, Single-Stranded / Q000378:metabolism; D004279:DNA, Viral / Q000378:metabolism; D004720:Endonucleases / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D007526:Isoelectric Point; D008274:Magnesium; D008345:Manganese; D011071:Poly T / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D011071:Poly T; D008345:Manganese; D011189:Potassium Chloride; D004720:Endonucleases; D008274:Magnesium