Deoxyribonuclease A of chick embryo. Partial purification and characterization of the enzyme.
A deoxyribonuclease has been purified 570-fold from the 14-day-old chick embryos. The purified enzyme requires Mg2+ or Mn2+ ions for maximum activity. The optimum pH is 9.0 in 20 mM Tris-HCl buffer. Its isoelectric point is 6.7. NaCl and N-ethylmaleimide strongly inhibit the reaction. An apparent molecular weight of 45,000 is determined by sedimentation in a glycerol density gradient. The enzyme hydrolyzes denatured DNA 50 to 100 times more rapidly than duplex DNA. RNA and synthetic polyribonucleotides are not substrate for the enzyme. DNase A catalyzes the endonucleolytic and exonucleolytic cleavages of single-stranded DNA. The enzyme produces DNA fragments having 70 to 100 nucleotides long at early time of reaction and then degrades these DNA fragments to acid-soluble materials, of which more than 70% is mononucleotides. In the exonucleolytic attack, the enzyme initiates hydrolysis of a single-stranded DNA from 5' to 3' direction. Chick embryo DNA-binding protein gives an intensive effect on the DNase A reaction by inhibiting the endonuclease activity rather than exonuclease activity under the standard assay conditions.
D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D002642:Chick Embryo; D004247:DNA / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D003851:Deoxyribonucleases / Q000302:isolation & purification* / Q000378:metabolism; D006868:Hydrolysis; D007526:Isoelectric Point; D008970:Molecular Weight; D013379:Substrate Specificity; D013997:Time Factors
D002413:Cations, Divalent; D004269:DNA, Bacterial; D004247:DNA; D003851:Deoxyribonucleases; C019328:deoxyribonuclease A