Potassium and Rubidium Effluxes in Saccharomyces cerevisiae

1985 ◽  
Vol 40 (9-10) ◽  
pp. 721-725 ◽  
Author(s):  
María D . Ortega ◽  
Alonso Rodríguez-Navarro
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ph Regulation ◽  
Uptake System ◽  
Acidic Ph ◽  
Efflux System ◽  
First Order ◽  
Ph Values ◽  
First Order Kinetics

Abstract In growing cells, K+ and Rb+ effluxes followed first order kinetics, took place with slight differences between K+ and Rb+ and were stimulated at acidic pH values. In uncoupled cells and ATP-depleted cells, K+ efflux was higher than Rb+ efflux. In ATP-depleted cells, the effluxes were not stimulated at acidic pH values. Two different K+ effluxes are proposed: (i) the normal efflux, which may be a K+/H+ antiport and does not function in ATP-depleted cells, and (ii) the backward reaction of the uptake system, which can be high in depolarized cells. The role of the normal efflux system in K+ content and pH regulation is discussed.

New insights on the UV/TiO2 photocatalytic treatment of thiomersal and its 2-sulfobenzoic acid product

2021 ◽  
Vol 02 ◽  
Author(s):  
Emmanuel M. de la Fournière ◽  
Jorge M. Meichtry ◽  
Graciela S. Custo ◽  
Eduardo A. Gautier ◽  
Marta I. Litter
Keyword(s):  
Degradation Products ◽  
Acidic Ph ◽  
Cosmetic Products ◽  
Acid Product ◽  
First Order ◽  
First Order Kinetics ◽  
Photocatalytic Destruction ◽  
Pseudo First Order ◽  
Mineralization Degree ◽  
Suitable Technique

Background: Thiomersal (TM), a complex between 2-mercaptobenzoic acid (2-MBA) and ethylmercury (C2H5Hg+), is an antimicrobial preservative used in immunological, ophthalmic, cosmetic products, and vaccines. Objective: TM has been treated by UV/TiO2 photocatalysis in the presence or absence of oxygen at acidic pH. C2H5Hg+, 2-MBA, and 2-sulfobenzoic acid (2-SBA) were found as products. A 2-SBA photocatalytic treatment was undertaken to study sulfur evolution. Methods: Photocatalytic runs were performed using a UVA lamp (λmax = 352 nm), open to the air or under N2. A suspension of the corresponding TM or 2-SBA salt and TiO2 was prepared, and pH was adjusted. Suspensions were stirred in the dark for 30 min and then irradiated. TM, 2-MBA, 2-SBA, and C2H5Hg+ were quantified by HPLC, sulfur by TXRF, and the deposits on the photocatalyst were analyzed by chemical reactions. The mineralization degree was followed by TOC. Sulfate was determined using BaCl2 at 580 nm. Results: Photocatalytic destruction of TM and total C2H5Hg+ was complete under N2 and air, but TM degradation was much faster in air. The evolution of TM and the products followed a pseudo-first-order kinetics. Conclusion: TiO2-photocatalytic degradation is a suitable technique for the treatment of TM and its degradation products. In contrast to other organomercurial compounds, TM degradation is faster in the presence of O2, indicating that the oxidative mechanism is the preferred pathway. A significant TM mineralization (> 60%, NPOC and total S) was obtained. TM was more easily degraded than 2-SBA. Sulfate was the final product.

scholarly journals The role of histidine-118 of inorganic pyrophosphatase from thermophilic bacterium PS-3

1991 ◽  
Vol 278 (2) ◽  
pp. 595-599 ◽  
Author(s):  
N Hirano ◽  
T Ichiba ◽  
A Hachimori
Keyword(s):  
Thermophilic Bacterium ◽  
Complete Loss ◽  
Inorganic Pyrophosphatase ◽  
Histidine Residue ◽  
First Order ◽  
Diethyl Pyrocarbonate ◽  
Lysyl Endopeptidase ◽  
First Order Kinetics ◽  
Pseudo First Order

Treatment of the inorganic pyrophosphatase from thermophilic bacterium PS-3 with diethyl pyrocarbonate resulted in the almost complete loss of its activity, which followed pseudo-first-order kinetics. The presence of Mg2+ prevented the inactivation. Enzyme inactivated with diethyl pyrocarbonate was re-activated by hydroxylamine. The inactivation parallelled the amount of modified histidine residue, and a plot of the activity remaining against the amount of modified histidine residue suggested that the modification of one of two histidine residues totally inactivated the enzyme. The site involved was found to be located in a single lysyl endopeptidase-digest peptide derived from the ethoxy[14C]carbonylated enzyme. Amino acid analysis and sequence analysis of the peptide revealed that it comprised residues 96-119 of the inorganic pyrophosphatase from thermophilic bacterium PS-3. These results, when compared with those reported for the Escherichia coli and yeast enzymes, imply that His-118 of the inorganic pyrophosphatase from thermophilic bacterium PS-3 is located near the Mg(2+)-binding site and thus affects the binding of Mg2+.

Saccharomyces cerevisiae glucose signalling regulator Mth1p regulates the organellar Na+/H+ exchanger Nhx1p

2010 ◽  
Vol 432 (2) ◽  
pp. 343-352 ◽  
Author(s):  
Keiji Mitsui ◽  
Masafumi Matsushita ◽  
Hiroshi Kanazawa
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Sole Carbon Source ◽  
Glucose Sensor ◽  
Ph Regulation ◽  
Gene Knockout ◽  
Carbon Sources ◽  
Acidic Ph ◽  
In Cells

Organelle-localized NHEs (Na+/H+ exchangers) are found in cells from yeast to humans and contribute to organellar pH regulation by exporting H+ from the lumen to the cytosol coupled to an H+ gradient established by vacuolar H+-ATPase. The mechanisms underlying the regulation of organellar NHEs are largely unknown. In the present study, a yeast two-hybrid assay identified Mth1p as a new binding protein for Nhx1p, an organellar NHE in Saccharomyces cerevisiae. It was shown by an in vitro pull-down assay that Mth1p bound to the hydrophilic C-terminal half of Nhx1p, especially to the central portion of this region. Mth1p is known to bind to the cytoplasmic domain of the glucose sensor Snf3p/Rgt2p and also functions as a negative transcriptional regulator. Mth1p was expressed in cells grown in a medium containing galactose, but was lost (possibly degraded) when cells were grown in medium containing glucose as the sole carbon source. Deletion of the MTH1 gene increased cell growth compared with the wild-type when cells were grown in a medium containing galactose and with hygromycin or at an acidic pH. This resistance to hygromycin or acidic conditions was not observed for cells grown with glucose as the sole carbon source. Gene knockout of NHX1 increased the sensitivity to hygromycin and acidic pH. The increased resistance to hygromycin was reproduced by truncation of the Mth1p-binding region in Nhx1p. These results implicate Mth1p as a novel regulator of Nhx1p that responds to specific extracellular carbon sources.

scholarly journals Stability of carotenoids toward UV-irradiation in hexane solution

2008 ◽  
Vol 73 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic
Keyword(s):  
Free Radical ◽  
Uv Irradiation ◽  
First Order ◽  
Chemical Structures ◽  
First Order Kinetics ◽  
Uv C ◽  
Hexane Solution

The stabilities of four selected carotenoids dissolved in hexane, two carotenes and two xanthophylls, toward UV-irradiation of three different ranges (UV-A, UV-B and UV-C) were studied in this work. The carotenoids underwent bleaching via a probable free radical mediated mechanism following first-order kinetics. The bleaching rates were highly dependent on the input of the involved photons and, although not consistently, on the chemical structures of the investigated compounds. For the two xanthophylls, a possible role of oxygen associated with their bleaching cannot be neglected.

scholarly journals Quantitative analysis of proton-linked transport system. β-Galactoside exit in Escherichia coli

1980 ◽  
Vol 188 (2) ◽  
pp. 467-473 ◽  
Author(s):  
I R Booth ◽  
W A Hamilton
Keyword(s):  
Escherichia Coli ◽  
Quantitative Analysis ◽  
Transport System ◽  
Rate Constants ◽  
The Other ◽  
First Order ◽  
First Order Kinetics ◽  
Solute Accumulation ◽  
External Ph

The exit of lactose and thiomethyl-beta-D-galactoside from Escherichia coli ML308-225 has been studied to determine the role of carrier-dependent (zero-trans efflux) and carrier-independent (leak) processes. On the basis of its sensitivity to p-chloromercuribenzene sulphonate the exit of lactose was found to be almost wholly mediated by the carrier. Consistent with this conclusion was the finding that the rate of exit of this sugar was dependent on the external pH, being considerably slower at acid pH. On the other hand exit of thiomethyl-beta-D-galactoside was found to be composed of both carrier-dependent and carrier-independent processes. Both processes exhibited first-order kinetics with the rate constants for zero-trans efflux and leak being 0.137 min-1 and 0.079 min-1, respectively. The relevance of these findings for out earlier proposal for the methods of attenuation of solute accumulation is discussed [Booth, Mitchell & Hamilton (1979) Biochem. J. 182, 687–696].

scholarly journals Degradation kinetics and in vitro digestive stability of selected bioactive compounds from a beverage formulated with butterfly pea flowers

2022 ◽  
Vol 52 (5) ◽  
Author(s):  
Renata Oliveira Santos ◽  
Laura Monteiro Keller ◽  
Vanessa Sales de Oliveira ◽  
Carlos Alberto Bucher ◽  
José Lucena Barbosa Junior ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Model Systems ◽  
First Order ◽  
Ph Values ◽  
First Order Kinetics ◽  
Butterfly Pea ◽  
Effects Of Temperature

ABSTRACT: This study evaluated the effects of temperature on the pH of extracts of ascorbic acid and anthocyanins from petals of butterfly pea, as well as their in vitro digestive stability in model systems at 60, 70, and 80 °C. The pH values significantly decreased with an increase in the temperature (P < 0.05). The findings were similar for the degradation of anthocyanins and ascorbic acid, which followed first-order kinetics in all the systems. The samples heated at 80 °C presented the highest degradation rate (kobs), as well as higher percentages of degradation at the end of digestive stability in vitro.

Role of pH on Metribuzin Dissipation in Field Soils

Weed Science ◽  
1976 ◽  
Vol 24 (5) ◽  
pp. 508-511 ◽  
Author(s):  
James S. Ladlie ◽  
William F. Meggitt ◽  
Donald Penner
Keyword(s):  
Soil Ph ◽  
Half Life ◽  
Residue Analysis ◽  
Soil Samples ◽  
First Order ◽  
First Order Kinetics ◽  
Field Soils ◽  
Pseudo First Order

Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] residue analysis of soil samples showed greater amounts of residue extractable at soil pH 6.7 than 4.6. Metribuzin leaching increased with increasing soil pH. Metribuzin disappearance from soil followed pseudo first-order kinetics. The half-life of metribuzin decreased as soil pH increased and increased at all soil pH levels as depth of sampling increased. The decreased activity and decreased rate of metribuzin dissipation at lower soil pH is apparently due to protonation and increased adsorption.

Contribution to the knowledge of the role of SH-groups in the molecule of pea alcohol dehydrogenase

1985 ◽  
Vol 50 (9) ◽  
pp. 2015-2020
Author(s):  
Noemi Čeřovská ◽  
Sylva Leblová
Keyword(s):  
Alcohol Dehydrogenase ◽  
Active Center ◽  
Protective Action ◽  
First Order ◽  
Sh Groups ◽  
Coenzyme Binding ◽  
First Order Kinetics ◽  
Sh Group ◽  
Pea Seeds

p-Chloromercuribenzoate irreversibly inactivates alcohol dehydrogenase (ADH) isolated from germinating pea seeds. The reaction follows the first order kinetics. The inactivation of pea ADH is pH-dependent and is maximal at pH 9.0. NAD protects the enzyme from inactivation by p-chloromercuribenzoate; the higher the concentration of the coenzyme and the longer the period of incubation of NAD with the enzyme, the lower the degree of inactivation. Ethanol does not prevent the enzyme from inactivation. o-Phenanthroline in a concentration of 1 . 10-3 mol l-1 decreases the degree of inactivation of the enzyme by p-chloromercuribenzoate by 20%; imidazole is without effect on the reaction. Zn2+-ions in concentration of 1 . 10-5 mol l-1 also partly protect the enzyme from inactivation by p-chloromercuribenzoate. The results obtained show that the SH-groups sensitive to labeling with p-chloromercuribenzoate are localized in the active center of the enzyme, probably in the coenzyme-binding site. The protective action of Zn2+-ions and of o-phenanthroline against this inactivation confirms the assumption that the SH-group acts as a zinc ligand in the active center of the enzyme.

scholarly journals Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

2020 ◽  
Vol 16 ◽  
pp. 509-514 ◽  
Author(s):  
Anna R Bockman ◽  
Jeffrey M Pruet
Keyword(s):  
Reaction Kinetics ◽  
Structural Features ◽  
Product Formation ◽  
Reaction Conditions ◽  
First Order ◽  
First Order Kinetics ◽  
Synthetic Utility ◽  
Pseudo First Order ◽  
Pteridine Derivatives

The synthetic utility of pterins is often hampered by the notorious insolubility of this heterocycle, slowing the development of medicinally relevant pteridine derivatives. Reactions which expedite the development of new pterins are thus of great importance. Through a dual role of diazabicycloundecene (DBU), 7-carboxymethylpterin is converted to the soluble DBU salt, with additional DBU promoting an ester-to-amide transformation. We have explored this reaction to assess its scope and identify structural features in the amines which significantly affect success, monitored the reaction kinetics using a pseudo-first order kinetics model, and further adapted the reaction conditions to allow for product formation in as little as 5 min, with yields often >80%.

scholarly journals Comparative Activity of Six Recombinant Stilbene Synthases in Yeast for Resveratrol Production

2020 ◽  
Vol 10 (14) ◽  
pp. 4847
Author(s):  
Nemesio Villa-Ruano ◽  
Antonio Rivera ◽  
Efraín Rubio-Rosas ◽  
Gerardo Landeta-Cortés ◽  
Jenaro Leocadio Varela-Caselis ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Batch Fermentation ◽  
Expression Vector ◽  
The Other ◽  
Acidic Ph ◽  
Polygonum Cuspidatum ◽  
Recombinant Yeast ◽  
Coumaric Acid ◽  
Comparative Activity

Resveratrol is a nutraceutical with relevant benefits to human health. This investigation reports on the generation and evaluation of six recombinant yeast lines that produce resveratrol from p-coumaric acid. The yeast lines contained a single p-coumaric acid-Co-A ligase from Plagiochasma appendiculatum combined with the stilbene synthases from Parthenocissus henryana, Polygonum cuspidatum, Morus alba var. atropurpurea, Rheum tataricum, Vitis vinifera and Arachis hypogaea. Codon optimized versions of these sequences were inserted in an expression vector flanked by the constitutive PGK and GPD promoters before expression in Saccharomyces cerevisiae. Batch fermentation (60 h) revealed that yeast lines had different capacities (p < 0.01) to produce resveratrol. Slightly acidic pH (6) and concentrations <100 mg L−1 p-coumaric acid improved resveratrol yields. Among the six lines, those containing the stilbene synthases (STS) from P. cuspidatum and M. alba produced up to 39 mg L−1 using 70 mg L−1 p-coumaric acid. On the other hand, lines expressing STS from V. vinifera, A. hypogaea and R. tataricum generated resveratrol faster than other lines but accumulated lower amounts at the end of the batch period (27–30 mg L−1). The simultaneous consumption of ethanol and p-coumaric acid corroborates the role of ethanol as a carbon source involved in the conversion of p-coumaric acid into resveratrol.

Sign in / Sign up

Export Citation Format

Share Document