• BMB Reports
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• v.31 no.1
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• pp.106-110
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• 1998

We have employed a DNA-native-polyacrylamide gel electrophoresis (DNA-native-PAGE) assay system to characterize the enzyme activity of the endonuclease secreted by human B lymphoblastic IM9 cells. Experimental results clearly demonstrated that the endonuclease activity of IM9 cell culture medium is distinct from that of DNase I in the DNA-native-PAGE assay system. Immunoprecipitation analysis using anti-DNase I antibody showed that the secreted endonuclease is not recognized by the antibody. The secreted endonuclease was estimated using supercoiled plasmid DNA as a substrate. The pH optimum required for the catalytic activity was determined to be in the range of pH 6.6-7.4. No significant difference in the endonuclease secretion was observed by stimulation of the IM9 cells with interferon-${\gamma}$ or interleukin-$1{\beta}$.

• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.316-319
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• 2021

Restriction endonucleases play an important role in molecular cloning, clinical diagnosis, and pharmacological drug studies. In this study, DNA-templated copper nanoclusters (DNA-CuNCs) were used to detect AluI endonuclease activity due to their high fluorescence emission and rapid synthesis of DNA-CuNCs under ambient conditions. Results showed that AluI activity was detected in a highly sensitive manner at low concentrations of AluI endonuclease by the fluorescence intensity of DNA-CuNCs. Additionally, its inhibition was monitored in the presence of daidzein under optimal conditions.

• Animal cells and systems
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• v.1 no.3
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• pp.451-455
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• 1997

The effects of nalidixic acid, mitomycin C, and cadmium chloride $(CdCI_2)$ on the activity of 8-hydroxyguanine $(oh^8Gua)$ endonuclease, a DNA repair enzyme for oxidatively modified guanine, $(oh^8Gua$ were studied. Nalidixic acid and mitomycin C, typical inducers of the S0S DNA repair response in E. coli, showed different effects. Nalidixic acid raised the activity of this enzyme, but mitomycin C did not show such an effect. Cadmium chloride also induced the enzyme activity, These results show that the expression of $oh^8$ Gua endonuclease is regulated by multiple factors and can be induced under stressful conditions. In an attempt to demonstrate the importance of this enzyme in defense against DNA damage and mutagenesis, we also characterized mutM mutant for its oh8 Gua endonuclease activity. The mutM mutant showed no detectable $oh^8$ Gua endonuclease activity, unlike its wild type showing high activity. In addition, paraquat, a superoxide producing compound, failed to elevate $oh^8Gua$ endonuclease activity in this mutant. These results suggest that the mutM gene is identical to the $oh^8Gua$ endonuclease gene of E. coli. Taken together with previous reports, these results suggest that $oh^8Gua$ endonuclease plays a crucial role in the protection of aerobically growing organisms from threats of oxidative DNA damage and mutation.

• BMB Reports
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• v.31 no.4
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• pp.405-408
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• 1998

Endonuclease-sensitive sites detected by T4 endonuclease V or UvrABC nuclease treatments were compared in the dihydrofolate reductase gene of UV-irradiated Chinese hamster ovary B-11 cells. The number of endonuclease-sensitive sites detected by T4 endonuclease V treatment followed by NaOH denaturation was twice that of formamide denaturation. Repeated treatment of damaged genomic DNA with T4 endonuclease V resulted in no further increase in the number of endonuclease-sensitive sites detected. The numbers of endonuclease-sensitive sites detected by UvrABC nuclease using each denaturation condition were similar. Sequential treatment with the two endonucleases using formamide denaturation resulted in twice the number of endonuclease-sensitive sites detected by treatment of each nuclease alone. Due to a lack of AP endonuclease activity these results suggest the presence of T4 endonuclease V-sensitive sites which could be complemented by alkaline gel separation or by UvrABC nuclease treatment.

• Microbiology and Biotechnology Letters
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• v.15 no.5
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• pp.352-355
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• 1987

The isolation and characterization of type II restriction endonuclease from Clostridium thermocellum ATCC 27405 were described. This enzyme (Cth I endonuclease) is an isoschizomer of Bcl I endonuclease recognizing 5'-TGATCA-3'. Cth I endonuclease requires MG$^{2+}$ ion for its activity and is maximally active at PH 1.5 to 10.5 in the Presence of 0 to 10mM NaCl. Cth I endonuclease is heat stable and has an optimum temperature of 6$0^{\circ}C$. The activity of Cth I enzyme is sensitive to dam methylation.

• Journal of Plant Biology
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• v.33 no.4
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• pp.293-301
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• 1990

We have purified and characterized a deoxyribonuclease from zygotes of the eukaryotic green alga, Chlamydomonas reinhardtii and investigated effects of the polyamines, putrescine, spermidine and spermine on the purifed endonuclease-catalyzed cleavage of plasmid DNA. The enzyme has a molecular weight of about 37 kDa as measured by gel filtration and SDS-polyacrylamide gel electrophoresis. There is no requirement for a divalent cation. The activity is sensitive to ionic strength, as NaCl and KCl result in inhibition. The cleavage of plasmid DNA by the purified endonuclease was effectively inhibited by polyamines. The enzyme activity was inhibited more effectively by spermine than by spermidine. The inhibition by putrescine was lower than the other two polyamines.

• BMB Reports
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• v.30 no.1
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• pp.66-72
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• 1997

A mammalian DNA repair enzyme, UV endonuclease III which also functions as a ribosomal protein S3 (rpS3), was purified from mouse cells and characterized. UV endonuclease III was previously cloned and known to yield a peptide of 32 kDa upon expression in E. coli [Kim et al., (1995) J. Bioi. Chem. 270, 13620-13629]. However, biochemically purified UV endonuclease III, which has a sedimentation coefficient of 3.25, appears to have an additional peptide of 28 kDa. It appears that two bands were derived from one complex, judging from the comparison of the nuclease activity on the native and SDS-gel electrophoreses. UV endonuclease III becomes non-specific upon purification and this phenomenon is more significant in the case of pure fractions of the enzyme. Non-specific activity was not influenced by pH or any salt conditions.

• Journal of Microbiology
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• v.38 no.2
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• pp.88-92
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• 2000

A human ribosomal protein S3 (rpS3), which also functions as a DNA repair enzyme(UV endonuclease III), was expressed in a methylotrophic yeast, Pichia pastoris, and biochemically characterized. UV endonuclease activity was preiously characterized, and this activity of mammalian rpS3 was found to be non-specfic upon purification and storage. Under the Pichia expression system, the subcloned cDNA of the human rpS3 gene revealed a peptide of 42 kDa by SDS-PAGE and Western blot. The secreted form of human rpS3 rendered no endonuclease activity while the intracellular form showed UV specific endonuclease activity by the nick circle assay.

• Korean Journal of Microbiology
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• v.25 no.1
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• pp.73-79
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• 1987

A restriction endonuclease, Kpn I has been isolated from Klebsiella pneumonia. Cells were broken by sonication. After ultracentrifugation the supernatant containing Kpn I activity was further purified by Sepharose-6B gel filtration, DEAD-Cellulose, Heparin-Agarose, and Aminohexyl-Agarose column chromatography. Final enzyme preparation was essentially free of contamination exonuclease and phosphatase, as judged by ligation-recut test. Total activity of the enzyme recovered from 10 grams of cells was $4.7\times 10^5$ units.

• Korean Journal of Microbiology
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• v.24 no.4
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• pp.406-410
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• 1986

The isolation and charateriation of a type II restriction endonuclease from Xanthomonas citri IFO 3835 were described. This enzyme (Xci I endonuclease) is an isoschizomer of Sal I endonuclease recognizing 5'-GTCGAC-3' and cleaving at the site indicated by the arrow. Unlike Sal I endonuclease, Xci I endonuclease requries a NaCl concentration of 50mM for its maximum activity.