Search results for "Transferase"
showing 10 items of 1030 documents
Enzymic Control of Reactive Metabolites from Aromatic Carcinogens
1980
Mutation and transformation in C3H 10T 1/2 mouse fibroblasts were coordinately induced by 4-nitroquinoline N-oxide and identically modulated by caffeine strongly suggesting mutation as one necessary step in the sequence of events ultimately leading to transformation. The enzymic control of reactive metabolites derived from aromatic carcinogens was then investigated using bacterial mutagenicity as an analytical tool. It was shown that the correlation of bacterial mutagenicity with carcinogenicity of BP and four major metabolites was substantially better when these compounds were activated by intact hepatocytes as compared to commonly used broken cell preparations which suggests that the rela…
Identification of the 3-amino-3-carboxypropyl (acp) transferase enzyme responsible for acp3U formation at position 47 in Escherichia coli tRNAs
2019
AbstracttRNAs from all domains of life contain modified nucleotides. However, even for the experimentally most thoroughly characterized model organism Escherichia coli not all tRNA modification enzymes are known. In particular, no enzyme has been found yet for introducing the acp3U modification at position 47 in the variable loop of eight E. coli tRNAs. Here we identify the so far functionally uncharacterized YfiP protein as the SAM-dependent 3-amino-3-carboxypropyl transferase catalyzing this modification and thereby extend the list of known tRNA modification enzymes in E. coli. Similar to the Tsr3 enzymes that introduce acp modifications at U or m1Ψ nucleotides in rRNAs this protein conta…
Mode of action of herbicidal derivatives of aminomethylenebisphosphonic acid. Part II. Reversal of herbicidal action by aromatic amino acids
1997
The herbicidal action of N-pyridylaminomethylenebisphosphonic acids is accompanied by an impairment of anthocyanin biosynthesis. This suggests that they might act as inhibitors of some steps in aromatic amino acid biosynthesis. Herbicidal effects were reversed by aromatic amino acids using both bacterial and plant models, a finding that strongly supports this hypothesis. Structural features of these compounds suggest the sixth enzyme in the shikimate pathway 5-enol-pyruvoylshikimate-3-phosphate (EPSP) synthase as a possible target, since a strong structural similarity exists between aminomethylenebisphosphonic acid and an inhibitor of EPSP synthase, the herbicide glyphosate. This is, howeve…
Mannosyl transferases inSaccharomyces cerevisiae: Evidence for the occurrence of ectomannosyltransferase activity
1981
The subcellular distribution of mannosyltransferases inSaccharomyces cerevisiae was studied following the separation of the plasma membrane from other intracellular membranous systems. Most of the activity was linked to internal membranes, and the rest was located at the level of the plasma membrane. Yeast plasma membranes coated on their external face with concanavalin A when incubated with GDP-[U-14C]mannose incorporated 20% less [U-14C]mannose in glycoproteins and 110% more in glycolipids than plasma membranes alone. This suggested that part of the total mannosyltransferase activity of the plasma membrane is located on its outer surface. A significant incorporation of radioactive mannose…
Immediate early response of the marine sponge Suberites domuncula to heat stress: Reduction of trehalose and glutathione concentrations and glutathio…
1997
The marine sponge Suberites domuncula was used to identify early markers for thermal stress. Cubes from sponges have been kept for 30 min at 31°C (10 °C higher than the ambient temperature). After this treatment the sponge cubes were kept again at 21°C. To demonstrate that the animals reacted to the elevated temperature, the expression of heat shock protein (HSP) was determined. Using an antibody raised against HSP70, it was found by Western blotting that the animals specifically express a 45 kDa polypeptide after heat treatment. It was shown that even after 10 min of heat treatment the steady-state concentration of trehalose drops by 40% from a base level of 13 nmol/mg protein. The activit…
Cell wall xyloglucan incorporation by xyloglucan endotransglucosylase/hydrolase in pine hypocotyls
2004
Abstract In the present study, we have examined the incorporation of labelled xyloglucan oligosaccharides into the cell wall xyloglucan of pine hypocotyl sections, and the effect of plant hormones on the incorporation and on XTH enzyme activity (EC 2.4.1.207). Xyloglucan heptasaccharide [ 3 H ]XXXGol was absorbed, transported and incorporated into the cell wall xyloglucan of de-rooted pine hypocotyls. Incorporation of [ 3 H ]XXXGol into soluble and cell wall xyloglucan was induced by IAA, brassinolides and XXXG in pine hypocotyl segments. A relationship between growth induction, by IAA, brassinolides and XXXG, and both soluble and cell wall-bound XTH was found. We suggest that IAA induced-g…
Enzymes as Regulators of Toxic Reactions by Electrophilic Metabolites
1979
Conversion of many compounds which are not electrophilically reactive as such to metabolites responsible for cytotoxic, mutagenic and/or carcinogenic effects is catalyzed by mammalian enzymes. Many reactive agents, whether metabolites or parent compounds, are also subject to inactivation by mammalian enzymes.
Bleomycin, a selective inhibitor of DNA-dependent DNA polymerase from oncogenic RNA viruses.
1972
Abstract Bleomycin, an antibiotic, inhibits the DNA-dependent DNA polymerase from Rauscher murine leukemia virus. Higher concentrations of BLM ∗ are required to inhibit it's RNA-dependent DNA polymerase. These inhibition effects of the non-competitive type are not altered by preincubation of the DNA with BLM. Under comparable conditions neither the DNA-dependent DNA polymerase activity from E. coli and mouse liver nor the DNA-dependent RNA polymerase activity from mouse lymphoma cells are affected by BLM.
Activity and kinetics of DNA dependent DNA and RNA polymerases n xeroderma pigmentosum and in normal human skin.
1971
1. DNA dependent DNA polymerase (E.C.2.7.7.7) was prepared from human normal and from Xeroderma pigmentosum skin. 2. DNA polymerase from normal skin has the same Michaelis constant with native and denatured DNA as templateKm= 120 ± 11 µg DNA/ml, with differing maximum reaction velocities. 3. The enzyme from Xeroderma pigmentosum has the same Michaelis constant for denatured DNA as the enzyme from normal skin, but with native DNA as template, theKmvalue is lower (97.2 ± 9.8). The maximum reaction velocities of the Xeroderma pigmentosum enzyme with native resp. denatured DNA as template are the same. 4. DNA dependent RNA polymerases (E.C.2.7.7.6) from normal and Xeroderma pigmentosum skin wer…
SULT1A1 gene deletion in BRCA2-associated male breast cancer: a link between genes and environmental exposures?
2013
SULT1A1, a member of sulfotransferase superfamily, is a drug and hormone metabolizing enzyme involved in the metabolism of a variety of potential mammary carcinogens of endogenous and exogenous origin. Interestingly, the metabolic activity of SULT1A1 can be affected by varia- tions in gene copy number. Male Breast Cancer (MBC) is a rare disease and less investigated disease compared to female BC (FBC). As in FBC, the concurrent effects of genetic risk factors, particularly BRCA2 mutations, increased exposure to estrogens and environmental carcinogens play a relevant role in MBC. By quantitative real-time PCR with TaqMan probes, we investigated the presence of SULT1A1 gene copy number variat…