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)

The cellular localization of enzymes in Diplococcus pneumoniae was examined by fractionation of spheroplasts. A deoxyribonuclease implicated in the entry of deoxyribonucleic acid (DNA) into the cell during genetic transformation was located in the cell membrane. This enzyme, the major endonuclease of the cell (endonuclease I), which is necessary for the conversion of donor DNA to single strands inside the cell and oligonucleotides outside, thus could act at the cell surface. Another enzyme, the cell wall lysin (autolysin), was also found in the membrane fraction. Other enzymes, including amylomaltase, two exonucleases, and adenosine triphosphate-dependent deoxyribonuclease, and a restriction type endonuclease, were located in the cytosol within the cell. None of the enzymes examined were predominantly periplasmic in location. Spheroplasts were obtained spontaneously on incubation of pneumococcal cells in concentrated sugar solutions. The autolytic enzyme appears to be involved in this process. Cells that were physiologically competent to take up DNA formed osmotically sensitive spheroplasts two to three times faster than cells that were not in the competent state. Although some genetically incompetent mutants also formed spheroplasts more slowly, other such mutants formed them at the faster rate.
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PMID:Membrane location of a deoxyribonuclease implicated in the genetic transformation of Diplococcus pneumoniae. 0 Mar 66

The major fraction of deoxyribonuclease activity from human urinary protein was purified 40-fold in about 14% yield. The enzyme shows an isoelectric point at pH 4.2 and has a molecular weight of 33,600+/-3,000. Optimum activity was shown at pH 6.8 in the presence of 12.5 mmol/l Mg2+ plus 1 mmol/l Ca2+. The enzymic reaction is inhibited by high ionic strength (greater than 300 mmol/l Na+). The purified enzyme readily hydrolyzes native DNA to oligodeoxyribonucleotides with an average chain length of 5.3+/-0.2 after exhaustive digestion. Therefore, this endonuclease may be designated as neutral deoxyribonuclease (deoxyribonucleate oligonucleotidohydrolase, EC 3.1.4.5).
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PMID:The major fraction of deoxyribonuclease activity from human urinary proteins. Purification and properties. 3 20

Three major alkaline deoxyribonuclease (DNase) activities have been identified in sorbose-containing liquid culture medium in which wild-type Neurosporacrassa were grown: DNase A, a Ca++dependent endonuclease of molecular weight 65,000 daltons which has no specificity for single- or double-stranded DNA (ss-DNA or ds-DNA) and no activity with RNA; DNase B, a Mg++-dependent single-strand specific exonuclease of molecular weight 78,000 daltons active with both ss-DNA and RNA; DNase C, a divalent metal ion-dependent endo-exonuclease of molecular weight 65,000 having single-strand specific endonuclease activity with ss-DNA and RNA and exonuclease activity with ds-DNA. Three mutants which were shown previously to have wide spectra of sensitivities to mutagens, and which exhibited reduced release of DNase activity on sorbose-containing agar test plates (the Nuh phenotype), were deficient relative to the wild-type in the release of these major alkaline DNases into the liquid culture medium. The uvs-3 mutant released only small amounts of DNase A and DNase C; nuh-4 did not release detectable DNase C and released only a very low level of DNase B; uvs-6 released only a low level of DNase A. A nuh mutant (nuh-3) which is not mutagen sensitive relative to the wild-type released low levels of DNase B. On the other hand, an ultraviolet light-sensitive mutant (nuc-2) which does not have the Nuh phenotype was normal in the release of these DNases.
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PMID:Alkaline deoxyribonucleases released from Neurospora crassa mycelia: two activities not released by mutants with multiple sensitivities to mutagens. 15 56

Over 95% of the deoxyribonuclease (DNase) activity of log-phase mycelia of Neurospora crassa is expressed as single-strand (ss) specific endonucleolytic activity. This activity is associated with three nucleases (D1, D2, and D3) which after partial purification from extracts, express activity with double-strand (ds) DNA as well. All three enzymes also degrade RNA at approximately the same rates that they degrade ss-DNA. D3 has been identified as endoexonuclease, an enzyme previously shown to have endonuclease activity with ss-DNA and RNA and exonuclease activity with ds-DNA, both of which are inhibited by ATP. D3 is inhibited by ATP, is relatively resistant to p-hydroxymercuribenzoate (PHMB), and sediments with an apparent molecular weight of 75 000. D2 has the properties of the previously described mitochondrial nuclease. It is a relatively unstable Mg2+-dependent endonuclease with no appreciable strand specificity for DNA. In addition, it is not inhibited by ATP and is strongly inhibited by PHMB and by the ethylenediamine tetraacetic acid (EDTA). It also sediments with an apparent molecular weight of 75,000. The properties of D1 are quite variable from one preparation to another. Freshly isolated D1 sediments with an apparent molecular weight of 180 000. It often shows some inhibition by ATP, but is relatively resistant to both PHMB and EDTA. However, on 'ageing,' the properties of D1 gradually convert to those of D2 with concomitant decrease in molecular weight, loss of inhibition by ATP, and increase in sensitivities to PHMB and EDTA. The results indicate that D1 is very likely a second form of the mitochondrial enzyme. Evidence was obtained for the presence of protein inhibitor(s) in crude extracts which may account for the masking of the ds-DNase activities of these enzymes in extracts. Two Rec-like mutants of Neurospora (uvs-3, and nuh-4) are deficient mainly inexpressed levels of D3, the endo-exonuclease. However, the levels of inactive endo-exonuclease precursor in these two mutants are higher than in the wild type. There may, therefore, be some defect in the conversion of precursor to active enzyme in these two mutants. Another mutant, which is not sensitive to mutagens relative to the wild (nuh-3), has depressed levels of both endo-exonuclease and the mitochondrial enzyme. Nuh-3 has some defect in the conversion of D1 to D2. Proteinases probably play some role in vivo in these enzyme conversions.
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PMID:The major intracellular alkaline deoxyribonuclease activities expressed in wild-type and Rec-like mutants of Neurospora crassa. 15 96

An endonuclease partially purified from human lymphoblasts, and active against ultraviolet-irradiated DNA, was found to act additionally on DNA damaged by either x-radiation or methylmethanesulfonate. To determine if these activities were truly endonucleolytic, the reaction products were analyzed under conditions that prevented conversion of apurinic or apyrimidinic sites to single-strand breaks. With either ultraviolet- or x-irradiated DNA, strand breakage remained maximal, hence confirming the endonucleolytic character of the enzyme. By contrast, with DNA alkylated with methylmethanesulfonate, strand breakage was sharply reduced. Additional experiments indicated that the activity for alkylated DNA induces strand breaks only in concert with a purified endonuclease specific for apurinic sites, suggesting that it is an N-glycosidase that depurinates alkylated bases. This enzyme was separated from the endonuclease specific for irradiated DNA, by chromatography on DNA-agarose.
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PMID:Characterization of human enzymes specific for damaged DNA: resolution of endonuclease for irradiated DNA from an apparent N-glycosidase active on alkylated DNA. 19 41

A deoxyribonuclease specific for methylated DNA was isolated from Diplococcus pneumoniae. The enzyme, an endonuclease, degrades DNA for Escherichia coli to fragments of average molecular weight about half a million; it forms discrete fragments from phage lambda DNA. Methyl-deficient E. coli DNA is not attacked, neither is DNA from Micrococcus radiodurans, which contains no methylated adenine or cytosine. Nor is DNA from D. pneumoniae or phage T7 attacked. However, DNA from M. radiodurans, D. pneumoniae, and T7 is attacked after methylation with and E. coli extract. Methylated T7 DNA is degraded to discrete fragments. Although the genetic transforming activity of normal DNA from D. pneumoniae is not affected by the enzyme, transforming activity of methylated DNA is destroyed. The enzyme is designated endonuclease R Dpn I. Under certain conditions another enzyme of complementary specificity can be isolated. This enzyme, designated endonuclease R Dpn II, produces a similar pattern of fragments from the DNA of T7 without prior methylation of the DNA. It also degrades normal DNA for D. pneumoniae. It is suggested that this pair of enzymes plays a role in some unknown control process, which would involve a large fraction of the specific base sequences that are methylated in E. coli DNA and are present but not methylated in DNA from other sources.
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PMID:A deoxyribonuclease of Diplococcus pneumoniae specific for methylated DNA. 23 9

A ribonuclease (ribonucleate 3-pyrimidine-oligonucleotidohydrolase, EC 3.1.4.22) was purified 8300-fold from soluble fraction of beef brain and its properties were investigated. The enzyme is an endonuclease capable of hydrolyzing tRNA, rRNA, poly(C), but shows no activity towards poly(U), poly(A), and poly(G). The preparation is free of deoxyribonuclease, non-specific phosphodiesterase and phosphomonoesterase activity. The enzyme has a pH optimum of 7.6, is not heat stable, has a molecular weight of 25 000, and has a K-m of 134 mu rRNA and K-m of 1600 mug poly(C) per ml.
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PMID:Purification of an alkaline ribonuclease from soluble fraction of beef brain. 23 61

A mutation of Diplococcus pneumoniae, end-1, reduces the major deoxyribonuclease activity of the cell, an endonuclease, to 10% of its normal value without impairing transformation. Further mutations, called noz, abolish the residual endonuclease activity and block transformation. The residual endonuclease is similar to the wild-type enzyme in size, charge, divalent cation dependence, inhibition by ribonucleic acid, and formation of oligonucleotide products. However, the mutant endonuclease is more temperature sensitive, which suggests that the end-1 mutation occurred in a structural gene for the enzyme. Genetic analysis showed that the noz mutations occur at the same genetic locus. A number of new end mutants were analyzed. Those that retained more than 1.4% of the normal endonuclease activity were essentially normal in transformation; those with less than 1% were defective. The transformation-defective end mutants appear to be blocked in the entry of deoxyribonucleic acid (DNA) since they carry out the prior step of binding DNA to the outside of the cell. The major endonuclease of the cell may act as a DNA translocase by attacking and degrading one strand of DNA, thereby facilitating entry of the complementary strand into the cell.
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PMID:Identification of a deoxyribonuclease implicated in genetic transformation of Diplococcus pneumoniae. 23 79

An endonuclease purified from Hemophilus influenzae made single strand breaks in DNA containing apurinic or apyrimidinic sites but had no detectable endonuclease activity on untreated native DNA. The new 5'-termini created at the cleavage sites were base-free deoxyribose 5-phosphate residues. The enzyme preparation also catalyzed the exonucleolytic release of 5'-mononucleotides from bihelical DNA and the hydrolysis of DNA 3'-terminal phosphomonoesters. The phosphatase-exonuclease activity was indistinguishable from that reported by Gunther and Goodgal (J. Biol. Chem. (1970) 245, 5341-5349) and resembled that of exonuclease III of Escherichia coli. The endonucleolytic and exonucleolytic activities could not be separated by electrophoresis, sedimentation, or gel filtration, and they were also affected simultaneously by mutation. The enzymatic activities appear to be functions of a single monomeric protein (M(r) = 30,000).
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PMID:A DNase for apurinic/apyrimidinic sites associated with exonuclease III of Hemophilus influenzae. 30 19

A DNA glycosylase was purified about 30-fold from cultured human lymphoblasts (CCRF-CEM line) and was found to cleave 3-methyladenine from DNA alkylated with methyl methanesulfonate. The enzyme did not promote the release of 1-methyladenine, 7-methyladenine, or 7-methylguanine from DNA nor did it act on denatured methylated DNA. It produced apurinic sites in DNA alkylated with N-methyl-N-nitrosourea and ethyl methane-sulfonate as well as methyl methanesulfonate but not in untreated DNA or in DNA alkylated with nitrogen mustard or irradiated with ultraviolet light or X-rays. The glycosylase was free of detectable endonuclease activity in experiments with untreated DNA or DNA exposed to ultraviolet light; low levels of endonuclease activity, obtained when X-irradiated, alkylated, or depurinated DNA was the substrate, were attributed to contaminant apurinic endonuclease activity. This 3-methyladenine-DNA glycosylase has an estimated molecular weight of 34,000, is not dependent on divalent metal ions, and shows optimal activity at pH 7.5--8.5.
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PMID:Partial purification and characterization of a human 3-methyladenine-DNA glycosylase. 42 Aug 22


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