title: Purification and characterization of DNase VIII. A 5'-3' directed exonuclease from human placental nuclei.
abstract: DNase VIII is an exonuclease purified from human placenta trophoblast nuclei. The enzyme has a pH optimum of 9.5 and requires a divalent cation. It is inhibited by salt and stimulated by Triton X-100. Glycerol gradient analysis of the activity indicates a sedimentation coefficient of 2.8 S (31,000 daltons if globular). This enzyme initiates hydrolysis from 5'-phosphorylated termini of single-stranded DNA and acts at internal phosphodiester bonds liberating 5'-phosphorylated oligonucleotides. It degrades polynucleotides of repeating base sequence as well as single-stranded DNA, yielding oligonucleotides of even number, in which the main reaction products are dinucleotides. The activity on denatured DNA is not inhibited by the presence of ultraviolet-induced photoproducts. DNase VIII can also initiate hydrolysis at those distorted termini produced by the action of Micrococcus luteus dimer specific endonuclease on duplex DNA, which contains cyclobutane dimers.
mesh_terms: D002467:Cell Nucleus / Q000201:enzymology*; D005090:Exodeoxyribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013379:Substrate Specificity
chemical_list: D005090:Exodeoxyribonucleases; C037210:DNase VIII; D008274:Magnesium