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, 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

A thermostable DNA polymerase was prepared from Bacillus caldotenax by using a four-step chromatography procedure. The protein exists as a monomer of M(r) 94,000, has a pI of 4.9 and has no associated 3'-5' or 5'-3'-exonuclease activities or endonuclease activity. The temperature optimum of the enzyme was about 70 degrees C and the pH for maximum activity was about 7.5. The enzyme has an absolute requirement for a bivalent cation, and maximum activity was obtained at the unusually high concentration of 70 mM-MgCl2. Mg2+ could be replaced by MnCl2 or CoCl2, with decreased activity, at the lower optimal concentrations of 1 mM and 2.5 mM respectively. Enzyme activity was inhibited in the presence of 2',3'-dideoxy-TTP, arabinosyl-CTP and aphidicolin. Enzyme activity was stimulated with KCl concentrations of about 100 mM, and concentrations of univalent salts above about 150 mM inhibited activity. The enzyme could use activated calf thymus DNA, poly(dA).p(dT)10 or primed single-stranded phage M13 DNA as a template and maximum activity was obtained with poly(dA).p(dT)10. The enzyme was inactive on unprimed single-stranded DNA, double-stranded DNA and polyribonucleotide template/primer. The apparent Km values for individual dNTPs, determined with the other dNTPs at saturating concentrations, were 5.7 microM (dCTP), 6.3 microM (dATP, dGTP) and 6.4 microM (dTTP). The Km value for the overall incorporation of each dNTP from an equimolar mixture of all four dNTPs was 24.7 microM. The kcat. value was about 1.05 s-1. The kcat./Km value was 0.16-0.18 M-1.s-1 for individual dNTPs and 0.04 for the incorporation of an equimolar mixture of all four dNTPs. Some of the properties of the enzyme show it may be classified as an alpha-Type DNA polymerase.
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PMID:Purification and properties of DNA polymerase from Bacillus caldotenax. 144 54

Escherichia coli endonuclease IV and its Saccharomyces cerevisiae homologue Apn1, two DNA repair enzymes for free radical damages, were previously shown to be inactivated by metal-chelating agents. In the present study, atomic absorption spectrometry of endonuclease IV revealed the presence of 2.4 zinc and 0.7 manganese atoms, whereas Apn1 contained 3.3 zinc atoms and no significant manganese. EDTA-inactivated endonuclease IV retained 0.7 zinc atom but little detectable manganese. ZnCl2 reactivated 1,10-phenanthroline-treated Apn1, but was ineffective with endonuclease IV treated with either 1,10-phenanthroline or EDTA. In contrast, enzymatic activity was restored to both enzymes after EDTA treatment by incubation with CoCl2 and to a lesser extent by MnCl2. Endonuclease IV, reactivated with CoCl2 or MnCl2, regained all of the activities characteristic of the native enzyme. MnCl2 was as effective as CoCl2 at restoring activity to the 1,10-phenanthroline-treated enzymes. The results indicate that intrinsic metals play critical roles in both endonuclease IV and Apn1 and that manganese may perform a special function in endonuclease IV. Possible mechanistic roles for the metals in these DNA repair enzymes are discussed.
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PMID:Metalloenzymes in DNA repair. Escherichia coli endonuclease IV and Saccharomyces cerevisiae Apn1. 172 Jul 75

In Chaetomium thermophilum (DSM 1495) within the mitochondrial DNA (mtDNA) small ribosomal subunit (rns) gene a group IIA1 intron interrupts an open reading frame (ORF) encoded within a group I intron (mS1247). This arrangement offers the opportunity to examine if the nested group II intron could be utilized as a regulatory element for the expression of the homing endonuclease (HEase). Constructs were generated where the codon-optimized ORF was interrupted with either the native group IIA1 intron or a group IIB type intron. This study showed that the expression of the HEase (in vivo) in Escherichia coli can be regulated by manipulating the splicing efficiency of the HEase ORF-embedded group II introns. Exogenous magnesium chloride (MgCl2) stimulated the expression of a functional HEase but the addition of cobalt chloride (CoCl2) to growth media antagonized the expression of HEase activity. Ultimately the ability to attenuate HEase activity might be useful in precision genome engineering, minimizing off target activities, or where pathways have to be altered during a specific growth phase.
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PMID:Using Group II Introns for Attenuating the In Vitro and In Vivo Expression of a Homing Endonuclease. 2690 94