The Mechanism of Action of AET: III. The Effect of Gamma Radiation on the Viscosity and the Enzymatic Activity of Urease Solutions

1961 ◽  
Vol 15 (5) ◽  
pp. 594 ◽  
Author(s):  
E. Anne Dickens ◽  
Bernard Shapiro
Keyword(s):  
Gamma Radiation ◽  
Enzymatic Activity ◽  
Mechanism Of Action

scholarly journals Mechanism of Action for HDAC Inhibitors—Insights from Omics Approaches

2019 ◽  
Vol 20 (7) ◽  
pp. 1616 ◽  
Author(s):  
Wenbo Li ◽  
Zheng Sun
Keyword(s):  
Clinical Trials ◽  
Enzymatic Activity ◽  
Histone Deacetylase ◽  
Mechanism Of Action ◽  
Histone Deacetylase Inhibitors ◽  
Catalytic Domain ◽  
Hdac Inhibitors ◽  
Mechanistic Studies ◽  
Low Toxicity ◽  
Strict Specificity

Histone deacetylase inhibitors (HDIs) are a class of prominent epigenetic drugs that are currently being tested in hundreds of clinical trials against a variety of diseases. A few compounds have already been approved for treating lymphoma or myeloma. HDIs bind to the zinc-containing catalytic domain of the histone deacetylase (HDACs) and they repress the deacetylase enzymatic activity. The broad therapeutic effect of HDIs with seemingly low toxicity is somewhat puzzling when considering that most HDIs lack strict specificity toward any individual HDAC and, even if they do, each individual HDAC has diverse functions under different physiology scenarios. Here, we review recent mechanistic studies using omics approaches, including epigenomics, transcriptomics, proteomics, metabolomics, and chemoproteomics, methods. These omics studies provide non-biased insights into the mechanism of action for HDIs.

A Novel Non-Competitive Chemical Proteasome Inhibitor Displays Preclinical Activity in Myeloma and Leukemia.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1711-1711
Author(s):  
Xiaoming Li ◽  
Tabitha E Wood ◽  
Remco Sprangers ◽  
Xinliang Mao ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
Cell Death ◽  
Tumor Cell ◽  
Enzymatic Activity ◽  
Mouse Models ◽  
Cell Lines ◽  
Mechanism Of Action ◽  
Proteasome Inhibitor ◽  
Proteasome Inhibitors ◽  
Leukemia Cells ◽  
Tumor Cell Lines

Abstract The proteasome is an enzymatic complex that rids cells of excess and misfolded proteins and possesses chymotrypin, trypsin, and caspase-like enzymatic activity. To date, all of the proteasome inhibitors approved for clinical use or in clinical trials inhibit the complex competitively by binding the active sites of the enzymes. Here, we report a novel chemical proteasome inhibitor that binds the alpha subunits of the 20S proteasome and inhibits the complex non-competitively through a dual copper-dependent and independent mechanism. In a screen of a focused chemical library for novel proteasome inhibitors, we identified 5-amino-8-hydroxyquinoline (5AHQ). When added to myeloma or leukemia intact cells or cell extracts, 5AHQ inhibited the enzymatic activity of the proteasome at low micromolar concentrations. In order to obtain further insight into the mechanism of action of 5AHQ, we carried out a kinetic analysis of inhibition of the enzymatic activity of purified T. Acidophilium proteasome. By Lineweaver-Burk plot analysis, 5AHQ inhibited the proteasome non-competitively. Next, we investigated the binding of 5AHQ to the proteasome. By NMR analysis, 5AHQ bound the half-proteasome complex comprised of a pair of α-rings, α7-α7, and clear spectral changes were observed that localized to residues Ile159, Val113, Val87, Val82, Leu112, Val89, Val134, Val24 and Leu136 inside the antechamber. In contrast, the competitive inhibitor MG132 that binds the proteolytic chamber did not produce any changes in spectra of α7-α7, as expected. 5AHQ bound copper in a 2:1 stoichiometry with a logβ′ value of 9.09, and the addition of copper to 5AHQ enhanced 5AHQ-mediated inhibition of the proteasome. However, binding intracellular copper was not sufficient to explain the effects of 5AHQ on the proteasome as analogues of 5AHQ that did not bind copper continued to inhibit the proteasome, copper-binding molecules not structurally related to 5AHQ did not affect the proteasome, and 5AHQ inhibited isolated proteasomes in buffers devoid of copper and other heavy metals. Given the effects of 5AHQ on the proteasome, we examined the effects of this molecule on the viability of leukemia and myeloma cell lines. Leukemia, myeloma and solid tumor cell lines were treated with increasing concentrations of 5AHQ for 72 hours and cell viability was measured by the MTS assay. 5AHQ induced cell death in 9/9 myeloma, 6/10 leukemia, and 3/10 solid tumor cell lines with an LD50 ≤5 uM. Cell death was confirmed by Annexin V staining. Consistent with its mechanism of action as a proteasome inhibitor, the ability of 5AHQ to induce cell death matched its ability to inhibit the proteasome. In addition, 5AHQ-mediated cell death was associated with inhibition of the NF-kappaB signalling pathway. As 5AHQ induced cell death in malignant cells, we evaluated the effects of oral 5AHQ in 3 mouse models of leukemia. Sublethally irradiated NOD-SCID mice were injected subcutaneously with OCI-AML2 or K562 human leukemia cells or intraperitoneally with MDAY-D2 murine leukemia cells. After tumor implantation, mice were treated with 5AHQ (50 mg/kg/day) or buffer control by oral gavage. Oral 5AHQ decreased tumor weight and volume in all 3 mouse models compared to control without causing weight loss or gross organ toxicity. In summary, we have identified a new strategy for inhibition of the proteasome and a lead for a new therapeutic agent for the treatment of hematologic malignancies.

Zur Strahleninaktivierung von Ribonuclease

1966 ◽  
Vol 21 (3) ◽  
pp. 224-231 ◽  
Author(s):  
Horst Jung ◽  
Helga Schüssler
Keyword(s):  
Molecular Weight ◽  
Gamma Radiation ◽  
Enzymatic Activity ◽  
Column Chromatography ◽  
Apparent Molecular Weight ◽  
Ribonuclease A ◽  
Nitrogen Atmosphere ◽  
The Other ◽  
Radiation Action ◽  
Higher Doses

Ribonuclease A was irradiated in water with 60Co gamma radiation, and the products formed were separated according to their molecular weight by column chromatography on Sephadex G-50. When the irradiations are carried out in nitrogen atmosphere aggregation to dimers and higher polymers is observed. An appreciable fraction of this aggregated component retains enzymatic activity. At higher doses the enzymatic activity of the aggregates is inactivated at the same rate as monomer ribonuclease A. Irradiation in air yields two components; one is equivalent to that found in nitrogen atmosphere, the other has an apparent molecular weight of about 20 000 but contains no enzymatic activity. This last component is not observed when methionine is present during irradiation. In methionine containing solutions all inactivited ribonuclease molecules exist in the form of dimers and polymers. Irradiation in the dry state leads to the same result. Consequently, every model designed to describe the radiation action on ribonuclease has to consider the fact that in solution, in the presence of a protecting agent, and in the dry state the loss of enzymatic activity is always accompanied by aggregation to products with increased molecular weight.

Zur Strahleninaktivierung von Ribonuclease

1968 ◽  
Vol 23 (7) ◽  
pp. 934-943 ◽  
Author(s):  
Horst Jung ◽  
Helga Schüssler
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Low Temperature ◽  
Gamma Radiation ◽  
Enzymatic Activity ◽  
Amino Acid Residue ◽  
Atomic Hydrogen ◽  
Active Components ◽  
Experimental Conditions ◽  
Elution Pattern

Dry ribonuclease was irradiated with 60Co gamma radiation in vacuo, under oxygen atmosphere, and at 77 °K. By chromatography on Sephadex G-50 active ribonuclease was separated from inactive radiation products. From the elution pattern and by ultracentrifugation it was shown that mainly unfolded dimers are formed by gamma irradiation of dry ribonuclease. Amino acid analysis of these various products shows that in all components cystine, methionine, tyrosine, phenylalanine, lysine, and histidine are destroyed with increasing dose whereas glycine shows a small increase. Thus, in ribonuclease irradiated in the dry state the same amino acids are changed as was found after irradiation in aqueous solutions. The radiosensitivity of dry ribonuclease shows an increase by the presence of oxygen of about 2 and a decrease at low temperature in vacuo of about 5. The same factors were also found for the alteration of amino acids, which means that under various experimental conditions amino acid destruction is proportional to loss of enzymatic activity of ribonuclease. The observed selectivity of amino acid destruction may be explained by energy migration or by the attack of atomic hydrogen liberated at random from the molecule. The total number of amino acids destroyed per ribonuclease molecule increases with dose. In enzymatically inactive products this value is always higher by one amino acid residue than in the active components. From this result and from the increase with dose it is concluded that after destruction of one amino acid residue the ribonuclease molecule has a probability (not depending on dose of irradiation) of 0.45 to become inactivated whereas in 55 per cent of all cases the molecule maintains its enzymatic activity.

scholarly journals Des-Aspartate-Angiotensin I Attenuates Mortality of Mice Exposed to Gamma Radiation via a Novel Mechanism of Action

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0138009 ◽  
Author(s):  
Hong Wang ◽  
Gautam Sethi ◽  
Weng-Keong Loke ◽  
Meng-Kwoon Sim
Keyword(s):  
Gamma Radiation ◽  
Mechanism Of Action ◽  
Angiotensin I

Inhibition of vascular cell growth by X-ray irradiation: comparison with gamma radiation and mechanism of action

2001 ◽  
Vol 50 (2) ◽  
pp. 485-493 ◽  
Author(s):  
Neal A Scott ◽  
Ian R Crocker ◽  
QiQin Yin M.S ◽  
Dan Sorescu ◽  
Josiah N Wilcox ◽  
...  
Keyword(s):  
Cell Growth ◽  
Gamma Radiation ◽  
Mechanism Of Action ◽  
Vascular Cell ◽  
X Ray

scholarly journals Characterization and evaluation of the enzymatic activity of tetanus toxin submitted to cobalt-60 gamma radiation

2021 ◽  
Author(s):  
Giselle Pacifico Sartori ◽  
Andréa da Costa ◽  
Fernanda Lúcio dos Santos Macarini ◽  
Douglas Oscar Ceolin Mariano ◽  
Daniel Carvalho Pimenta ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Enzymatic Activity ◽  
Tetanus Toxin

Mutations in TERT, the Gene Encoding Telomerase Reverse Transcriptase, in “Acquired” Aplastic Anemia Inhibit Enzymatic Function by a Dominant Negative Mechanism of Action.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3-3
Author(s):  
Rodrigo T. Calado ◽  
Hinh Ly ◽  
Hiroki Yamaguchi ◽  
Gabriela M. Baerlocher ◽  
Sachiko Kajigaya ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Reverse Transcriptase ◽  
Aplastic Anemia ◽  
Mechanism Of Action ◽  
Telomerase Activity ◽  
Dominant Negative ◽  
Telomerase Reverse Transcriptase ◽  
Wild Type ◽  
Gene Encoding ◽  
Tert Expression

Abstract About one third of patients with acquired aplastic anemia (AA) have very short telomeres of their peripheral blood leukocytes; short telomeres correlate to long disease duration and poor response to immunosuppressive therapy. We have recently shown that some cases of apparently “acquired” AA have mutations in TERC, the gene encoding the RNA component of telomerase (Fogarty et al., Lancet2003;632:1628; Yamaguchi et al., Blood2003;102:916). In the current study, we examined TERT, the gene encoding the telomerase reverse transcriptase, by sequencing the gene’s exons and proximal promoter region in peripheral blood DNA samples from 122 patients with AA and 282 controls. Four novel nonsynonymous mutations among five patients, not present in controls, were discovered; three polymorphisms were identified, two nonsynonymous SNPs and one deletion of a single amino acid. To investigate the functional consequences of the mutations, telomere lengths of leukocytes were assessed by flow cytometric fluorescence in situ hybridization (flow-FISH). All patients carrying TERT mutations had markedly short telomeres compared to age-matched controls, as opposed to other AA patients with polymorphisms, whose telomeres were normal. In one patient’s kindred, presence of the TERT mutation in other family members correlated to telomere shortening; non-carriers had normal telomeres. Telomerase function in patients’ T cells, activated by phytohemagglutinin and interleukin-2 to increase enzymatic activity, was measured by the telomeric repeat amplification protocol (TRAP). In all mutant AA patients evaluated, cell lysates yielded very low or no telomerase activity, as compared to normal controls. We cloned the AA-related mutations into a TERT expression vector and co-transfected these vectors into VA13 cells (with a TERC-containing vector, as this cell line does not have telomerase activity due to absent TERC and TERT expression). All mutant TERT-containing cell lysates were severely deficient in enzymatic activity. TERT gene expression, as evaluated by Northern blot, was normal in cells transfected with the mutated genes. When vectors containing wild-type TERT and individual TERT mutations were cotransfected, telomerase activity was dramatically reduced, in comparison to transfection of wild-type TERT vector only. These results indicate a dominant negative mechanism of action of TERT mutations as responsible for the absence of telomerase activity in AA patients’ cells. Family members lacking telomerase activity have short telomeres but appear physically normal and have no hematological abnormalities. In a provisional model of the telomere repair complex and marrow failure, mutations in DKC1 and the stability regions of TERC cause dyskeratosis congenita, with early presentation and associated physical anomalies. Mutations that affect the enzyme-binding region of TERC and in TERT, the reverse transcriptase itself, lead to a constitutionally reduced stem cell compartment and appear to be genetic risk factors for the development of “acquired” aplastic anemia.

scholarly journals Application of ionising radiation for the stabilisation of Trichoderma viride cellulases

2011 ◽  
Vol 23 (No. 3) ◽  
pp. 111-115
Author(s):  
V. Plaček ◽  
K. Vacek ◽  
J. Káš ◽  
K. Demnerová ◽  
J. Zídková ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Enzymatic Activity ◽  
Bacterial Contamination ◽  
Trichoderma Viride ◽  
Cellulase Activity ◽  
Dose Interval ◽  
Cellulolytic Enzymes ◽  
Activity Assay ◽  
Original Solution ◽  
Enzyme Preparations

The solutions of cellulolytic enzymes designated as standards for the cellulase activity assay were exposed in sealed glass ampoules (containing at least 100 Cx-units per ml in 30% w/w glycerol) to gamma radiation within the dose interval of 0–18 kGy. Glycerol was found to be the best enzyme stabiliser, however, the dose for the decontamination had to be increased in comparison with the original solution because glycerol protected also the contaminating microflora. The preparation after such treatment (30% of glycerol, dose 7 kGy) retained about 95% of the initial enzymatic activity without any decrease taking place in the following 6 months. The loss of the side activities did not exceed 10.5% and no bacterial contamination was detected either after 6 months of storage following the irradiation. No difference was found in the immunoreactivity of cellulases or in protein chromatografic (FPLC) pattern between the original and the irradiated enzyme preparations.  

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