Thymus deoxyribonuclease

Deoxyribonuclease II, DNase H, pancreatic DNase II, acid DNase, calf thymus attid DNase, spleen acid DNase (EC 3.1.22.1) a monomeric enzyme (M, 31,(XK>) which catalyses the endonucleolytic cleavage of double stranded DNA to 3 -phosphomononu-cleotides and 3 -phosphooligonucleotides The earliest definitive studies were performed on the enzyme from hog spleen, which became known simply as hog-spleen enzyme . But the enzyme (or enzymes with extremely amilar properties) is widely distributed in animal cells, including, e.g. human pancreas, thymus, liver, gastric mucosa and cervix, as well as crab testis, snails and salmon testis. Although optimal activity occurs at pH 4-S, this optimum is not sharply defined, and considerable activity is retained even at neutral pH. 

Deoxyribonucleic Acid, Since only carbons 3 and 5 of the 2-deoxyribose are available for esterification in DNA, the linkages are all most probably of the 3, 5 -type. Purified phosphodiesterase quantitatively liberates 5 -mononucleotides from thymus DNA 100), On the other hand, no method has as yet been developed for degradation of these nucleic acid to 3 -deoxy-mononucleotides, although the pyrimidine 3, 5 -diphosphates have been isolated from acid hydrolyzates of DNA. Crystalline pancreatic deoxyribonuclease rapidly degrades DNA to very low molecular weight polynucleotides, but identification of many of these products reveals no certain route for the action of the enzyme 168),... 

The enzyme, polymerase, has been purified more than 2000-fold from extracts of E, cdi, and has been studied in other bacteria, tumor cells, and calf thymus (370). In spite of extenave purification the E. eoli enzyme is not homogeneous and has not been freed of traces of deoxyribonucleases. However a net syntheas of DNA has been obtiuned, twentyfold more than added primer DNA. Synthesis can be measured by incorporation of radioactive deoxynucleotides into an add insoluble fraction (DNA). 

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