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PubMed2001

Transport measurements across Caco-2 monolayers of different organic and inorganic selenium: influence of sulfur compounds.

The transport and uptake of the most common Se compounds, selenate (SeO42-), selenite (SeO3(2-)), selenomethionine, and selenocystine, were investigated using confluent monolayers of Caco-2 cells, a human carcinoma cell line. Comparative measurements were performed in the absorptive (apical to basolateral side) and exsorptive (basolateral to apical side) directions. Apparent permeability coefficients (Papp), calculated from transport experiments in the absorptive direction, showed increasing values in the following rank order: about 1 x 10(6) cm/s < mannitol < SeO3(2-) < or = selenocystine < selenomethionine < SeO4(2-) < or = about 16 x 10(4) cm/s. The ratios of the Papp measured in the absorptive versus exsorptive directions indicated that only the organic forms presented a net polarized transport (Papp ratio >> 1), suggesting the presence of a transcellular pathway. No significant excretion was observed. The transport of selenomethionine was inhibited by its sulfur analog, methionine, suggesting a common transport mechanism. In contrast, an inhibition of the transport of selenocystine by cysteine was not observed. From the two substrates tested, sulfate and thiosulfate, only thiosulfate inhibited the transport of SeO4(2-) . This effect was also observed for SeO32- (i.e., was unspecific), which questioned the assertion of a common transport for sulfate and SeO4(2-) and may confirm the paracellular pathway of SeO42- suggested by the Papp ratio of about 1. The addition of glutathione (GSH) in large excess had no consequence on the passage of SeO3(2-) but strongly increased the uptake (about fourfold). The liquid chromatography - mass spectrometry (LC-MS) data showed that, in the ionic condition of incubation medium, GSH promptly reduced SeO3(2-) (< or = 2 min) in its elemental form Se0, which cannot ascribe to selenodiglutathione a direct role in the effect of GSH.

Biological Transport↗
PubMed1981

Metabolism of sulfur compounds by whole filaments and heterocysts of Anabaena variabilis.

Filaments of the heterocyst-forming cyanobacterium Anabaena variabilis reproduced 35SO4(2)-, incorporating 35S into cysteine, methionine, glutathione, sulfolipid, and several unidentified metabolites. The majority of the incorporated label accumulated in reduced glutathione. Heterocysts isolated from labeled filaments contained the same major labeled products. Isolated, metabolically active heterocysts were unable to reduce 35SO4(2)-, but were able to incorporate 35S2- into cysteine and glutathione. The results suggest that the initial activation of SO4(2)- occurs in vegetative cells and that some reduced forms, possibly including S20, are translocated into heterocysts.

Cyanobacteria↗
PubMed1982

Effect of various sulfur compounds on the transport system enzymes in human erythrocyte membranes.

We investigated the action of radioprotective agents: sodium S-(4-ethylphenylcarbonylmethylene)-thiosulfuric acid (SEPT), 2-(4-chlorophenyl)-thiazolidine (CPT) and dimethylsulfoxide (DMSO), on Na+/K+ATPase and Mg2+ATPase activity. SEPT inactivated more strongly Mg2+ATPase than Na+/K+ATPase, CPT dissolved in DMSO inhibited the activity of Mg2+ATPase, but did not affect that of Na+/K+ATPase. DMSO alone increased the activity of Mg2+ATPase and inhibited that of Na+/K+ATPase. Thus DMSO and CPT seem to act antagonistically on the activity of ATPases. The results indicate that radioprotectants strongly affect ATPases participating in membrane transport.

Acetophenones↗
PubMed1988

Effect of methotrexate on homocysteine and other sulfur compounds in tissues of rats fed a normal or a defined, choline-deficient diet.

Methotrexate (MTX) affects homocysteine (Hcy) metabolism in both cultured cells and patients, and this may be explained by a lack of the 5-methyltetrahydrofolate required for salvage of Hcy to methionine. We here report the effect of MTX on Hcy in serum and Hcy, S-adenosylhomocysteine (AdoHcy), S-adenosylmethionine (AdoMet) and reduced glutathione (GSH) in tissues of rats fed either a normal or a defined, choline-deficient (CD) diet. The CD diet alone did not affect the amounts of Hcy in serum and tissues, but decreased the amount of AdoMet in most tissues and increased the GSH content in the liver. MTX increased the amount of Hcy about 2-fold in serum, liver and kidney, and decreased the amount of AdoMet in liver and kidney, whereas the AdoHcy content in these tissues was essentially unaffected. Accordingly, both choline deficiency and MTX treatment reduced the AdoMet to AdoHcy ratio. The increased GSH in the liver induced by CD diet seemed to be abolished by MTX. In the spleen MTX had only a marginal effect on the Hcy and AdoMet content and decreased the GSH content. It is concluded that the increase in serum Hcy during MTX exposure probably reflects a disturbance of the Hcy metabolism in some tissues, and especially in the liver. Altered metabolism of other sulfur-containing metabolites may only partly be related to the inhibition of Hcy salvage, and some metabolic effects of MTX may be modulated by tissue-specific metabolic pathways as well as by the diet.

Analysis of Variance↗
PubMedDate not supplied

[Growth of Ectothiorhodospira shaposhnikovii on media with various sulfur compounds].

Ectothiorhodospira shaposhnikovii, strain 1, can use thiosulphate, sulphide, sulphite, sulphate, cystein, methionine and glutathione as a source of sulphur during its growth in the light and in the dark. Thiosulphate, sulphide and sulphite are used by the bacterium also as electron donors in photosynthesis so that it can grow in anaerobic autotrophic conditions. Growth of the cultures in the presence of various sulphur compounds depends on the concentration of sodium and potassium salts in the medium, particularly when the bacteria grow in the light and in the dark under aerobic conditions in the presence of such sulphur sources as sulphate, cysteine or methionine. The cells of E. shaposhnikovii produce thiosulphate reductase independent of a source of sulphur and growth conditions. The activity of sulphite reductase can be detected when the cells are cultivated in the presence of sulphates. The activity of APS-reductase has not been found in the cells grown under different conditions.

Aerobiosis↗
PubMed1983

The effect of dietary and sulfur compounds in alleviating 3-methylindole-induced pulmonary toxicity in goats.

The present experiment was designed to determine the effect of tissue concentrations of glutathione (GSH) and GSH-S-transferase activity on 3-methylindole (3MI)-induced pulmonary toxicity in vivo. Forty goats were given high protein, normal protein, high cysteine, high sulfate or diethyl maleate (DEM) to vary tissue concentrations of GSH before i.v. infusion of 3MI. The severity of lung lesion was scored. Tissue GSH concentration, GSH-S-transferase activity and cytochrome P-450 content were measured. Compared to goats fed normal protein diet, high cysteine or high sulfate increased the tissue GSH levels and reduced the severity of the lung lesion induced by 3MI. Pretreatment with DEM, by which the tissue GSH was depleted, increased the severity of 3MI-induced lung lesion. Tissue GSH-S-transferase activity was not changed. These results indicate that the tissue concentration of conjugating agents play an important role in 3MI-induced lung disease.

Animals↗
PubMed1975

Protective action of ascorbic acid and sulfur compounds against acetaldehyde toxicity: implications in alcoholism and smoking.

Acetaldehyde is a toxic substance common to heavy drinking of alcohol and heavy smoking of cigarettes. It has been implicated thereby in diseases of the cardiovascular, respiratory, and central nervous systems. Protection against acetaldehyde toxicity (i.e. anesthesia and lethality) was studied in rats by oral intubation of test compounds 30-45 minutes prior to oral intubation of a standardized oral LD 90 dose (18 millimoles/kilogram) of acetaldehyde. Animals were monitored for anesthesia (loss of righting reflexes) and lethality for 72 hours. A total of 18 compounds was tested. L-ascorbic acid at 2 millimoles/kilogram (mM/kg) showed moderate protection against anesthesia and marked protection against lethality. Greatest protection against anesthesia and lethality was obtained at 2 m M/kg with each of the following: L-cysteine, N-acetyl-L-cysteine, thiamin-HCl, sodium metabisulfite, and L-cysteic acid. A combination of L-ascorbic acid with L-cysteine, and thiamin-HCl at reduced dose levels (2.0, 1.0 and 0.3 mM/kg, respectively) gave virtually complete protection. A detailed literature review is presented of the rationale and significance of these findings. Our findings could point the way to a possible build-up of natural protection against the chronic body insult of acetaldehyde arising from heavy drinking of alcohol and heavy smoking of cigarettes.

Acetaldehyde↗
PubMed1975

Regulation of arylsulfatase synthesis by sulfur compounds in Klebsiella aerogenes.

In Klebsiella aerogenes, arylsulfatase synthesis was repressed by inorganic sulfate, sulfite, sulfide, thiosulfate, and cysteine, but not by methionine under normal growth conditions. We isolated cysteine-requiring mutants (Cys minus), and mutants (AtsS minus, AtsR minus) in which the regulation of arylsulfatase synthesis was altered. In the cysteine auxotroph, enzyme synthesis was also repressed by inorganic sulfate or cysteine. Kinetic studies on mutants of the cysteine auxotroph showed that inorganic sulfate repressed arylsulfatase synthesis and that this was not due to cysteine formed by reduction of sulfate. Arylsulfatase synthesis in the AtsS minus mutant was not repressed by inorganic sulfate but was repressed by cysteine. This mutant strain had a normal level of inorganic sulfate transport. Another mutant strain, defective in the inorganic sulfate transport system, synthesized arylsulfatase in the presence of inorganic sulfate but not in the presence of cysteine. The AtsS minus mutant could synthesize the enzyme in the presence of inorganic sulfate but not cysteine. The AtsR minus mutant could synthesize the enzyme in the presence of either inorganic sulfate or cysteine. These results suggest that there are two independent functional corepressors of arylsulfatase synthesis in K. aerogenes.

Biological Transport, Active↗
PubMed1995

Influence of 2,3-dimercaptopropanol and other sulfur compounds on oxophenylarsine-mediated inhibition of glucose uptake in MDCK cells.

Trivalent monosubstituted organoarsenicals, e.g., oxophenylarsine (PhAsO), exert various detrimental effects on mammalian cells. In addition to their well known interference with pyruvate and ketoglutaric acid oxidation, the effect on other cellular functions such as uptake of glucose may contribute to their acute toxicity. Different effects of PhAsO on insulin-stimulated and insulin-independent uptake of hexoses in various tissues have been reported. It has been shown previously that PhAsO inhibits the stereospecific uptake of glucose in MDCK cells. In this work, the insulin dependence of glucose uptake in these cells and the effects of 2,3-dimercaptopropanol (BAL), dithiothreitol (DTT) and 2-mercaptoethanol (ME) on PhAsO-induced inhibition of glucose uptake were investigated. A 200 mumol l-1 concentration of insulin had no measurable effect on cellular 14C accumulation from D-[6(-14)C]glucose, indicating an insulin-independent hexose transport system. In the presence of 2 mumol l-(-1) of PhAsO, glucose uptake was lowered to less than 50% of controls within 30 min. Greater inhibition was observed with higher concentrations of PhAsO, but cell viability as assessed by formazan formation started to decrease at concentrations > or = to 5 mumol l-1, especially after longer exposure times. When BAL was added in a ten-fold molar excess 30 min after beginning incubation with PhAsO (2 mumol l-1, virtually complete recovery of inhibited glucose uptake occurred within 10 min after addition. ME at up to a 100-fold molar excess over arsenic had no influence on the inhibition of glucose uptake within 120 min after addition.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Purification and properties of multiple isoforms of a novel thiol methyltransferase involved in the production of volatile sulfur compounds from Brassica oleracea.

Five functional isoforms of a novel plant thiol methyltransferase from the leaves of cabbage (Brassica oleracea L.) were purified to electrophoretic homogeneity. Pooled, partly purified preparations of the enzyme were previously shown to methylate thiol compounds released upon the hydrolysis of glucosinolates. The enzyme could also accept halide ions as substrates. The estimated molecular masses of the purified isoforms ranged between 26 and 31 kDa. The three most abundant isoforms of the enzyme could all catalyze the S-adenosyl-l-methionine-dependent methylation of thiocyanate, a number of organic thiols and iodide. However, the kinetic properties of these forms toward various substrates differed widely. None of the isoforms examined methylated the O- and N-equivalents of the thiol substrates. The three isoforms also had distinct pH optima, covering the range from 5 to 9. Their kinetic analysis indicated that they shared a sequential substrate binding mechanism and an Ordered Bi Bi mechanism for substrate binding and product release. Partial internal amino acid sequence from one isoform showed high similarity to an Arabidopsis EST of unknown function, and to a recently cloned methyl chloride transferase from Batis maritima. The differences in the pH optima and kinetic properties of the isoforms suggest that each may methylate a specific substrate or a narrow group of substrates under cellular conditions.

Brassica↗
PubMed1989

[The Maillard reaction. 18. Radical inhibition of browning by sulfur compounds].

ESR spectroscopic investigations on the mechanism of Maillard-reactions using the model D-glucose/glycine show radical formation in some of the reaction steps. These are possibly due to competitive reactions against ionic mechanism. The formation of radicals depends on the concentration of reactants and reaches a maximum in thermically induced browning reactions. The addition of L-cysteine leads to a decrease in the radical concentration to about 60%. It can be indirectly proven that the radicals are involved in the formation of browning products. The hyperfine structures of ESR spectra are supposed to be similar to pyrazine cation radicals.

Cysteine↗