Alkaline DNase Research Articles

Studies on chloroplast development and replication in Euglena: II. Identification of two different deoxyribonucleases

Extracts of Euglena contain at least two DNases. One, referred to as “Euglena acid DNase,” has a pH optimum of 4.6, and exhibits enzymic and purification properties similar to DNase II-like enzymes. The second DNase, referred to as “Euglena alkaline DNase,” has a pH optimum of 9.4, requires Ca 2+, and acts preferentially on heat-denatured DNA. Euglena alkaline DNase is either absent, present in low activity, or inhibited in dark-adapted cells; in addition, the activity of this DNase increases during light-induction of chloroplast development. We hypothesize that Euglena alkaline DNase is a chloroplast-related enzyme.

Nucleases activity in different segments of the human digestive tube compared to the incidence of carcinomas (histochemical study).

The alkaline and acid DNase and RNase activity was histochemically investigated in biopsies from the human digestive tube. Activity of these enzymes in the mucosal epithelium in different segments of the digestive tube was compared to the statistical incidence of malignant tumors deriving from this tissue (carcinomas). It was found that the alkaline and acid nucleases activity was very intense in small intestine precisely in this segment where the incidence of carcinomas was low, whereas the low activity of these enzymes in the stomach and large intestine corresponded to the high incidence of carcinomas. This observation confirmed our previously elaborated hypothesis, according to which the low activity of nucleases in normal tissues appeared to be a predisposing factor for malignant transformation. It could be also supposed that the nucleases constitute some kind of double barrier mechanism protecting the genetical stability of the cell against foreign nucleic acid incorporation or production; alkaline nucleases being an extracellular and acid nucleases an intracellular barrier.

A new DNA-exonuclease in cells infected with herpes virus: partial purification and properties of the enzyme.

SUMMARY Infection of BHK 21 (C 13) or HEp-2 cells with herpes virus was followed by a marked increase in the activity of alkaline DNase which was prevented by actinomycin D and puromycin. Activation of a latent enzyme was not responsible for the increase. The properties of the DNase appearing after virus infection in both cell types were the same, but they differed from those of the enzyme from uninfected cells in specificity towards the secondary structure of the DNA substrate, heat-stability, requirement for thiol groups, inhibition by K+ and Na+ ions and response to various concentrations of Mg2+ and Mn2+. The activities of acid DNase and alkaline phosphomonoesterase were not significantly altered after herpes infection. Further, the activity of alkaline RNase was not altered by infection, and this implies that the induced DNase was specific for DNA. The new DNase could be separated from the DNase present in uninfected cells and from alkaline phosphomonoesterase by chromatography on columns of DEAE-cellulose; its enzymic properties were the same as those observed with soluble extracts of cells infected with herpes virus.

Two deoxyribonucleases from Novifoff ascites hepatoma cells.

Two DNases have been isolated and separated from Novikoff ascites hepatoma by ammonium sulfate fractionation and have been further purified by chromatography on ion-exchange columns of DEAE types.The partially purified acid DNase is free of any measurable RNase activity, while the partially purified alkaline DNase preparation still exhibits RNase activity.The alkaline DNase requires sulfhydryl compounds for maximum activity, whereas the acid DNase does not. Both DNases require Mg2+ ions for maximum activity. EDTA strongly inhibits the alkaline DNase activity and the inhibition can be reversed by the addition of Mg2+ ions. On the other hand, EDTA activates the acid DNase either in the presence or in the absence of Mg2+.Sarkomycin inhibits the alkaline DNase but does not inhibit the acid DNase. Actinomycin D and heparin inhibit both DNase activities.The products of the alkaline DNase digestion consist of four deoxymononucleotides as well as higher oligonucleotides, all terminating in 5′-phosphate. The alkaline DNase seems to exhibit an endonucleolytic mode of attack in the early stage of hydrolysis with a subsequent exonucleolytic action. However, the possibility of contamination by an unknown exonuclease cannot be ruled out. On the other hand, the products of the acid DNase digestion consist mainly of oligonucleotides with average chain length larger than 8 units all terminating in 3′-phosphate. No mononucleotides can be detected. This suggests that the acid DNase is a typical endonuclease and possesses no detectable exonuclease activity.The acid DNase preferentially attacks linkages of the type dPupGp, whereas the preferential linkage(s) for the alkaline DNase has not been established.

Deoxyribonucleases from rat brain.

Abstract—Two distinctly different DNases were isolated from rat brain and could be separated easily by ammonium sulphate fractionation. One of the DNases acts optimally at pH 5.0 hydrolysing preferentially native DNA and requiring an optimal Mg2+ concentration of about 0.03 m. The other DNase has its optimal pH between 7.4 and 8.9, acts preferentially on heat‐denatured DNA and requires a lower Mg2+ concentration, the optimum being 1 × 10−4m.Cerebellum from adult rat brain has a lower acid DNase activity and higher alkaline DNase activity, and therefore has a higher ratio of alkaline DNase to acid DNase than the other areas of brain studied. This unique activity ratio in cerebellum of adult rat brain was not observed in infant rat brain.

The Effect of a Single Systemic X-Irradiation of the C57BL Mouse on the Nucleodepolymerases of the Thymus

In a study of thymic nucleodepolymerases in radiation-induced thymoma in the C57BL mouse, we noted that early postirradiation changes in activity appeared to be independent of the carcinogenic process. A detailed study of these early changes with low doses of X-irradiation was carried out as described in this paper. Nucleodepolymerase changes in mammalian tissues after whole-body X-irradiation have been reported. After 600 r to rats, there were variable changes in acid and alkaline RNase2 concentrations in whole-liver homogenates and liver mitochondria and depression of a soluble inhibitor tested with pancreatic RNase. These changes were noted 1 to 5 days after treatment (1). A twoto threefold increase in acid DNase concentration of spleen was found 24 hours after doses of 50 to 500 r to rats. The increase was not observed at earlier periods tested, and there was no change in spleen content (2, 3). Finally, increases in urinary (4) and serum (5) acid and alkaline DNases have been observed after 700 r to rats. The response of other enzymes of spleen and thymus to whole-body irradiation has been reviewed by DuBois and Petersen (6). Thymic concentration of various respiratory enzymes showed little or no change. The most marked effect observed was an increase in concentration of adenosinetriphosphatase after relatively small doses of X-irradiation to the rat. The increase was maximal in both spleen and thymus 3 to 5 days postirradiation with doses as low as 50 r in spleen and 100 r in thymus. It was two to three times normal in both tissues after 200 r (6). After 650 r to the mouse, however, splenic content of adenosinetriphosphatase was below normal from about 4 hours to 18 days (7).