Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An endonuclease which hydrolyzes depurinated DNA has been isolated from Phaseolus multiflorus enbryos; it has a molecular weight around 40,000. The enzyme is specific for apurinic sites; it has no action on normal DNA strands or on alkylated sites, and is without exonulcease activity. The rate of phosphoester bond hydrolysis near apurinic sites is far greater in native than in denatured DNA. The endonuclease is not inactivated by 10 mM EDTA, but is activity is however stimulated by Mg2+ or Mn2+. Its optimum pH is 7.5 to 8.0, and its optimum temperature 40degrees although, at this temperature, it is rapidly denatured; even low NaCl concentrations inhibit the enzyme activity. The endonuclease for apurinic sites of P. multiflorus is a non-histone protein of chromatin; the properties (like thermosensitivity of susceptibility to ionic strength) of the enzyme in situ, working on chromatin DNA, might be different from those described for the isolated endonuclease in homogenous aqueous solution.
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PMID:Purification and properties of a plant endonuclease specific for apurinic sites. 1 91

An endonuclease was detected in strains of Salmonella typhimurium containing the drug resistance plasmid pKM101. The enzyme was not detectable in strains lacking this plasmid, but it was present in strains containing mutants of pKM101 that were no longer able to enhance host cell mutagenesis. The endonuclease had a molecular weight of roughly 75,000 and, at pH 7.0, was equally active on single-stranded and duplex deoxyribonucleic acid (DNA). The reaction with single-stranded DNA was optimal at pH 5.5, whereas with duplex DNA the optimum was pH 6.8. The enzyme required a divalent cation for activity, and it had no detectable exonuclease activity with single-stranded or duplex DNA. The endonuclease extensively degraded DNA with no apparent base specificity, forming 5'-phosphomonoester termini. Although characterization of the endonuclease has not revealed its function, the enzyme does not appear to be a restriction endonuclease.
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PMID:Characterization of an endonuclease associated with the drug resistance plasmid pKM101. 1 40

Rat liver particulate neutral ribonuclease (EC 3.1.4.22) was extensively purified (up to 40000-fold). It is shown to be an endonuclease, specific for pyrimidine bases, hydrolysing 5'-phosphate ester bonds. The enzyme specificity, Km, pH optimum, stability in acid medium and thermal stability at high temperature are the same as those of rat pancreatic and serum ribonucleases. Like pancreatic and serum neutral ribonucleases, the hepatic enzyme is sensitive to the liver natural inhibitor. This inhibitor was purified 8000-fold; its association with ribonuclease follows zero-order kinetics. These identical properties for ribonuclease of rat liver, pancreas and serum support the hypothesis [Bartholeyns, Peeters-Joris & Baudhuin (1975) Eur. J. Biochem. 60, 385-393] of an extrahepatic origin for the liver enzyme, the plasma ribonuclease of pancreatic origin being taken up by endocytosis in the liver. Neutral ribonuclease activity was detected in all rat organs investigated; its distribution among tissues is different from the distribution of the natural ribonuclear inhibitor.
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PMID:Purification of rat liver particulate neutral ribonuclease and comparison of properties with pancreas and serum ribonucleases. 1 11

Acid ribonuclease, free of nucleases and phosphatases, is isolated from rat thymus chromatin. The pH optimum of the enzyme is 5.0-5.5, optimal concentrations of Na+ and K+ ions are 0.05-0.15 M and 0.05 M respectively, Mg2+ inhibits the enzyme activity. The enzyme hydrolyses poly U, poly AU, cytoplasmic and nuclear RNAs, but does not attack poly A, polyG, polyC, poly A:poly U, native and denatured DNA'S. The enzyme is 3'-endonuclease, it splits the bond between the 5'-carbon atom of adenosine, guanosine and uridine and 3'-phosphate of uridilic residue. Middle length of oligonucleotides after the hydrolysis of cytoplasmic RNA comprises 10 nucleotides. Possible role of the enzyme in the processing of nuclear RNAs is discussed.
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PMID:[Characteristics of acid ribonuclease from rat thymus chromatin]. 1 99

An endonuclease, present in the microplasmodia of Physarum polycephalum, has been partially purified from isolated nuclei by DEAE-cellulose and Sephadex G-75 chromatography. 1. The endonuclease produced single-strand scissions in double-stranded DNA which resulted in the generation of 5'-phosphoryl and 3'-hydroxyl termini. No activity was observed with single-stranded DNA as substrate. 2. The pH optimum was approximately 8.5. 3. Divalent cations were essential for enzyme activity. MnCl2 and MgCl2 gave maximal activity. CaCl2, ZnCl2 or CoCl2 did not activate the enzyme. 4. The endonuclease activity was highly sensitive to monovalent cations. 5. Endonuclease activity was found in two forms after gel filtration: an activity in a homogeneous peak with a molecular weight of approx. 20 000, and an activity that had a heterogeneous molecular weight and which was isolated in a complex with DNA. A possible function of the endonuclease in DNA replication is discussed.
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PMID:Endonuclease activity in nuclei of Physarum polycephalum. Partial purification and characterization. 2 Jan 46

Endonucleases from Micrococcus luteus that induce single-strand breaks in gamma-irradiated DNA have been separated chromatographycally into two groups. The first group involves two different enzymes: AP-endonuclease II (mol. weight 30 000) and AP, UV-endonuclease I (mol. weight 15 000) that recognize alkali-labile lesions in gamma-irradiated DNA and apurinic sites in DNA heated at 70 degrees C, pH 6.08 AP-endonuclease II in cooperation with DNA polymerase from M. luteus and T4 phage-induced polynucleotide ligase is capable of carrying out in vitro complete excision repair of alkali-labile lesins in gamma-irradiated DNA. The second group involves gamma-endonucleases X and Y that act on alkalistable gamma-ray lesions. gamma-endonucleases X and Y can be separated by chromatography on DEAE-cellulose but possess similar properties. Activity of gamma-endonucleases toward gamma-irradiated DNA is inhibited by only heavily UV-irradiated DNA (15 000 ergs/mm2). The data are consistent with the hypothesis that gamma-endonucleases are specific for thymine glycols (t' and tUV) in UV- and gamma-irradiated DNA.
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PMID:[Analysis of the activity of Micrococcus luteus endonucleases with respect to gamma-irradiated DNA]. 2 Jan 61

Evidence has been found on an alkaline endonuclease activity in the cytoplasmic and nuclear fraction isolated from the thymus and spleen mice. The chromatin-associated endonuclease activity was identified only in the spleen. The enzyme(s) was active on both single- and double-stranded DNA, but the reaction was faster if single-stranded DNA was used as a substrate. Maximum activity was found in the pH range of 7.9 to 8.1 in the presence of 10 mM Mg2+ and 1 mM Ca2+. The enzyme(s) splits DNA, yielding 3'-hydroxyl terminated polynucleotides. It is suggested that this alkaline endonuclease(s) is responsible for the formation of deoxyribopolynucleotides in the thymus and spleen of irradiated mice.
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PMID:Alkaline endonuclease(s) activity in the thymus and spleen of normal and irradiated mice. 2 4

Transfection has been found and characterized in pneumococcus. For replicating omega3 phage DNA extracted from infected cells, transfection was relatively efficient and rose linearly with DNA concentration and quadratically with time, according to T(T - 3.5) min(2). For mature DNA extracted from phage particles, transfection was hardly detectable below 1 mug/ml but increased about as the cube of the DNA concentration up to 100 mug/ml, and was still rising at concentrations over 200 mug/ml. The kinetics suggest a dependence on a mixed cubic function of the time of exposure of cells to mature DNA. Cell and phage DNAs competed with each other for transformation and transfection. Transfection was reduced much more strongly than transformation in cells that were deficient in the membrane-bound endonuclease required for conversion of donor duplex DNA to intracellular single strands; these data agree with the kinetic data in implying that independent entry of segments of two strands is necessary for transfection by replicating omega3 phage DNA and entry of at least three strands is necessary for transfection by mature DNA. To reconcile differing DNA concentration dependences of transfection and transformation with a common entry path, it was necessary to reexamine data on transformation and to recognize that this process continued to rise slowly through the concentration region usually described as "plateau." These results and the transfection data reflect multiple binding and nicking events that occurred on the cell surface before entry. Our conclusion is that transfection in pneumococcus occurs by association inside the cell of segments of single strands of phage DNA that have entered independently, creating gapped structures that need repair synthesis to create infective centers. Physical recombination is therefore automatically a prerequisite to transfection.
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PMID:Transfection in pneumococcus: single-strand intermediates in the formation of infective centers. 2 40

The DNAase in human urine was purified about 30-fold with a recovery of 28%. This involved DEAE-cellulose and phosphocellulose chromatography steps and gel filtration on Sephadex G-75. The enzyme required divalent cations such as Co2+, Mg2+, Mn2+ and Zn2+ for activity, but Ca2+, Cu2+ and Fe2+ were ineffective. EDTA and G-actin inhibited the reaction. The maximum activity was observed at pH 5.5 in acetate buffer plus Co2+ or Mg2+ and Ca2+. It had a molecular weight of approximately 38 000, estimated by gel filtration on Sephadex G-75 and isoelectric point of around pH 3.9. The enzyme is an endonuclease which hydrolyzes native, double-stranded DNA about 3 to 4 times faster than thermally denatured DNA to produce 5'-phosphoryl- and 3'-hydroxyl-terminated oligonucleotides. The final preparation was free of non-specific acid and alkaline phosphatases, phosphodiesterase and ribonuclease activities.
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PMID:Purification and properties of deoxyribonuclease from human urine. 2 31

An acid endonuclease hydrolyzing both DNA and RNA was purified from Tetrahymena pyriformis, strain E. The enzyme is distributed in all major subcellular compartments and is excreted into the growth medium towards the middle of the logarithmic phase. It hydrolyzes DNA to penta or hexanucleotides, on the average, bearing the monoesterified phosphate at the 3'-position. Particularly in early phases of the reaction it shows a very pronounced specificity for bases with a keto group at position 4 of the pyrimidine ring, such as guanine and thymine.
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PMID:Studies of the catalytic properties of an endonuclease isolated from Tetrahymena pyriformis. 2 34


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