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PubMed1995

Influence of thiols on the chlorinating effect of a myeloperoxidase system.

The structure-activity relationships for the interactions of a number of sulfhydryl compounds on the transformation of (Z)-3-(4-bromophenyl)-3-(3-pyridyl)allylamine (CPP 200) by an MPO-H2O2-Cl-(-)system at pH 5.25 have been studied. It was found that the inhibitory effect of the thiol group was strongly dependent on the presence of an electron-withdrawing NH3(+)-group in the molecule. Also, the acid-base properties of the thiolic compounds were involved in the inhibitory mechanisms.

Acids↗
PubMed1960

Reduction of radiation sensitivity of dry bacterial spores with hydrogen sulfide.

Hydrogen sulfide redtuces the lethal effect of x-rays in dry spores by about 50 percent when given after irradiation, and by approximately 75 percent when present during irradiation. The first effect is the result of removal of radicals that are toxic when combined with oxygen; the second, the removcal of radicals that become toxic in the absence of oxygen. With these results we construct an explanation of the action of sulfhydryl compounds in protection against radiation damage.

Bacteria↗
PubMed1990

Generalized rash induced by sulfhydryl drug in guinea pigs--a comparative study on it with cephalothin-induced rash in guinea pigs.

Adverse reactions produced by sulfhydryl compounds with active thiol groups have generally formed a distinctive pattern in man when they are viewed as a class. It has been reported that cutaneous SH-induced drug eruptions have a wide variety of clinical presentations; histologically, they show a pattern of eosinophilic necrosis and/or satellite necrosis similar to that seen in cutaneous graft vs host reactions. In the present experiments, guinea pigs were sensitized with cephalothin (CET) and thiol compounds such as tiopronin (TP), D-penicillamine, gold sodium thiomalate or thiomalate, using a method similar to that described previously. In lymphocyte stimulation tests, lymph node cells from the sensitized animals responded positively to spleen cells pulsed with each thiol compound. Intracutaneous tests revealed some positive reactions to each thiol compound; there was a tendency to produce a tuberculin type reaction with indurated erythema rather than the Jones-Mote type seen in CET-induced reactions. The dose-requirements for positive intracutaneous tests and generalized rash (GR) due to thiol compounds were lower than for CET, which required relatively large doses. Histologically, infiltration of basophilic cells was prominent in the skin lesions induced by intracutaneous tests with CET and in those of CET-induced GR. On the other hand, intracutaneous tests with TP following the induction of TP-induced GR revealed eosinophilic degeneration of epidermal cells, which was similar to the eosinophilic necrosis seen in cutaneous GVHR. Intracutaneous tests after the induction of CET-GR did not show any eosinophilic changes in the epidermal cells. These findings are reminiscent of the characteristics of eruptions induced by thiol compounds in man, which differ from the eruptions induced by CET.

Animals↗
PubMed1997

S-nitrosothiols inhibit neuronal norepinephrine transport.

Although it has been recently shown that nitric oxide (NO) and its congeners (NO(x)), including nitrosothiols, may modify catecholamine turnover in the brain, it is not known whether NO(x) affect norepinephrine (NE) uptake by sympathetic neurons. The nitrosothiol NO donor S-nitroso-acetylpenicillamine (SNAP, 100 microM for 1 h) elicited a concentration-dependent reduction in desipramine-sensitive [3H]NE uptake into PC-12 cells (66 +/- 3%; P < 0.01) or cultured rat superior cervical ganglia (74 +/- 5%; P < 0.001), whereas desipramine-insensitive [3H]NE uptake was unaffected, indicating a selective effect on uptake-1-mediated transport. Short-term coculture of PC-12 cells with microvascular endothelial cells expressing the cytokine-inducible NO synthase (NOS2) also exhibited a reduction in [3H]NE uptake (33 +/- 3%, P < 0.001) that could be prevented by the addition of the NOS inhibitor N-monomethyl-L-arginine (L-NMMA, 1 mM). Endogenous production of NO(x) by nerve growth factor-pretreated PC-12 cells also exhibited an L-NMMA-inhibitable reduction in [3H]NE uptake. Whereas SNAP resulted in a 10-fold elevation of PC-12 guanosine 3',5'-cyclic monophosphate (cGMP) content (P < 0.01), its effect on [3H]NE uptake was not mimicked by exposure to 8-bromo-cGMP. However, the inhibitory effect of SNAP on uptake-1-mediated [3H]NE transport could be attenuated by 1 mM cysteine, a sulfhydryl compound that could act as a sink for NO(x)-mediated nitrosation reactions, although cysteine did not affect the increase in intracellular cGMP with SNAP. These data suggest that an endogenous NO(x) source(s) modifies the activity of the uptake-1 catecholamine transporter in postganglionic sympathetic neurons, which, as we demonstrate, express both NOS1 and NOS3 isoforms, possibly by S-nitrosothiol-mediated nitrosation of regulatory sites on the transporter.

Animals↗
PubMed1983

Quantitative analysis of DNA-cleaving activities of macromomycin, auromomycin, and their free chromophores, and some DNA-binding characteristics.

The in vitro DNA-cutting activities of macromomycin (MCR), auromomycin (AUR), and their free chromophores were quantitatively analyzed by agarose gel electrophoresis of radioactive supercoiled pBR322 DNA. Methanol extract (chromophore) of MCR inhibited growth of cultured L5178Y cells and caused DNA strand scission without addition of reducing agents, whereas MCR required dithiothreitol (DTT) for its DNA cleavage. In the absence of DTT, concentrations of MCR chromophore, AUR and AUR chromophore to induce 50% degradation of form I DNA were 320 micrograms eq./ml, 44 micrograms/ml and 60 micrograms eq./ml, respectively. DTT stimulated DNA breakage by the drugs to a similar degree (ca. 4-fold). Since both chromophores showed the same biological activity, further studies were performed with AUR and its free chromophore. DNA strand breakage by AUR occurred rapidly and completed in 5 minutes. The rate of strand scission did not significantly change in a range of pH 7.0 to 10.5, but gradually declined below pH 7.0. Of 4 sulfhydryl compounds tested, DTT and cysteine exhibited potent stimulation, but glutathione and 2-mercaptoethanol weak or no enhancement. The DNA-cleaving activity of AUR and its free chromophore is blocked by addition of ethidium bromide, suggesting that the chromophore binds to DNA by an intercalation mechanism. Addition of poly[dG], poly [dG] X poly[dC], poly [dG-dC] X poly[dG-dC] or poly[dA-dT] X poly[dA-dT] protected DNA against degradation by AUR. Differential protecting effects of synthetic polynucleotides suggest that the chromophore shows higher affinity for guanine than for adenine, cytosine and thymine, and binds preferentially to a purine-pyrimidine neighboring sequence.

Animals↗
PubMed1978

Lactoperoxidase, peroxide, thiocyanate antimicrobial system: correlation of sulfhydryl oxidation with antimicrobial action.

The antimicrobial activity of the lactoperoxidase, peroxide, thiocyanate system against Escherichia coli was directly related to the oxidation of bacterial sulfhydryls. Lactoperoxidase catalyzed the oxidation of thiocyanate, which resulted in the accumulation of hypothiocyanite ion, OSCN-. A portion of the bacterial sulfhydryls were oxidized by OSCN- to yield sulfenic acid and sulfenyl thiocyanate derivatives. The remaining sulfhydryls were not oxidized, although OSCN- was present in large excess. The oxidation of sulfhydryls to sulfenyl derivatives inhibited bacterial respiration. This inhibition could be reversed by adding sulfhydryl compounds to reduce the sulfenyl derivatives and the excess OSCN-. Also, this inhibition could be reversed by washing the cells so as to remove the excess unreacted OSCN-. After washing, the bacteria underwent a time-dependent recovery of their sulfhydryl content. This recovery resulted in recovery of the ability to respire. The inhibited cells were viable if diluted and plated shortly after the incubation with the lactoperoxidase, peroxide, thiocyanate system. On the other hand, long-term incubation in the presence of the excess OSCN- resulted in loss of viability. Also, the inhibition of respiration became irreversible. During this long-term incubation, the excess OSCN- was consumed and the sulfenyl derivatives disappeared.

Dithiothreitol↗
PubMed1998

Quantitative determination of biological sulfhydryl groups by postcolumn derivatization and elucidation of microheterogeneity of serum albumins.

A quantitative analytical system for biological sulfhydryl compounds has been developed using an ion-pair reagent with isocratic elution and an on-line postcolumn derivatization with Ellman-type reagents. As human or bovine serum albumin has 35 cysteinyl residues, one cysteinyl residue exists as a free sulfhydryl moiety, and this gives rise to the microheterogeneity in serum albumin. Here we report for the first time the quantitative characterization of the microheterogeneity of serum albumin. Cysteine was found to be the major molecule attached to the sulfydryl group of the serum albumins. Although glutathione could not be detected, the Cys-Gly element of glutathione was found. Freshly prepared human serum albumin from healthy volunteers contained 0.46 nmol of Cys/mL of serum, 0.24 nmol of Cys-Gly/mL of serum, and very small amounts of glutathione (0.02 nmol/mL).

Adult↗
PubMed1980

A model for the activation and inactivation of neocarzinostatin, an antitumor protein.

Sulfhydryl compounds specifically activate and inactive neocarzinostatin as measured by the in vitro strand scission of T2 DNA. This effect, and evidence for strained disulfides in the molecule, leads us to propose a model of activation and inactivation. We suggest that neocarzinostatin reacts with sulfhydryl reagents to produce a short-lived active form which may react with DNA or proceed irreversibly via a conformational change to an inactive form (preneocarzinostatin). Three parameters of neocarzinostatin activity (inactivation rate, single strand break plateau position, and initial single strand break rate), have been measured for various sulfhydryl concentrations, and the observed results agree well with values expected from a simplified mathematical treatment of the model, thus supporting the assumptions made.

Antibiotics, Antineoplastic↗
PubMed1982

[Antiradical activity and sulfhydryl group concentration in normal and tumor tissue].

In cytosol of normal and tumor tissues obtained from rats and hamsters, antiradical activity (ARA) of bioantioxidants was assayed by the method of Glavind, while the content of sulfhydryl groups by the method of Ellman. ARA of normal tissues (liver, kidneys, stomach, large intestine, femoral muscles) was lower than the content of free SH-groups. The difference between the magnitudes under consideration was always negative in all the test tissues. In tumors of the liver, stomach, kidneys, large intestine and femoral muscle induced in rats and hamsters by chemical carcinogens, there was an increase in ARA from 21 to 125.8% as compared with respective normal tissues. The difference between ARA and the content of SH-groups in the tumors was always positive. It might be assumed that in normal tissues, ARA is primarily determined by sulfhydryl compounds. Meanwhile, apart from SH-containing compounds, the other substances also take part in the control of ARA.

Animals↗
PubMed1980

Tryptophan hydroxylase. The role of oxygen, iron, and sulfhydryl groups as determinants of stability and catalytic activity.

Tryptophan hydroxylase (EC 1.14.16.4) from rat mid-brain is inactivated upon exposure to oxygen. The degree of inactivation is dependent both on the temperature and partial pressure of oxygen to which the enzyme is exposed. Furthermore, molecular oxygen, and not an oxygen or hydroxyl radical, is responsible for the inactivation. Sulfhydryl compounds and reductants partially protect the hydroxylase from inactivation by oxygen. Enzyme inhibited by oxygen can be reconstituted by anaerobic incubation in the presence of dithiothreitol and Fe2+ at 25 degrees C and in some experiments the inclusion of inorganic sulfide, in addition to dithiothreitol and Fe2+, led to even greater recoveries of activity. Preincubation of tryptophan hydroxylase with various sulfhydryl reagents or disulfide compounds also produces inactivation which can be rapidly reversed by dithiothreitol. The substrate tryptophan protects the enzyme from inactivation by sulfhydryl reagents and disulfides but not from inactivation by oxygen. Finally, the enzyme was inhibited by a variety of iron chelators. These results suggest that the catalytic activity of tryptophan hydroxylase is dependent on the oxidation-reduction status of--SH groups and iron sites, which are probably located at the catalytic (substrate binding) site of the enzyme.

Animals↗
PubMed1980

Dietary modification of thyroxine deiodination in rat liver is not mediated by hepatic sulfhydryls.

The enzymatic deiodination of thyroxine (T(4)) is thiol dependent. Fasting (72 h) depresses hepatic T(4) deiodination and lowers the hepatic content of nonprotein sulfhydryls (NP-SH) and reduced glutathione (GSH). It has been proposed that the fasting effect may be mediated through these alterations in hepatic sulfhydryls. To test the importance of tissue (hepatic) thiol content in the modification of T(4) deiodination consequent to dietary manipulation, we examined the sequential deiodination of T(4) to 3,5,3'-triiodothyronine (T(3)) (5'-deiodination) and 3,3',5-triiodothyronine (reverse T(3), rT(3)) (5-deiodination) in liver homogenates without added thiol from groups of rats fed Purina lab chow (P) (a protein-rich diet), glucose alone (G), or glucose plus cysteine (G(c)) for 72 h or fasted (F) for the same period. The initial rate of each reaction was compared to the tissue concentrations of NP-SH and GSH. Dietary manipulation induced significant changes in hepatic deiodination of T(4) to T(3) and rT(3) and sulfhydryl content. There was a marked dissociation between the rate of each reaction and hepatic NP-SH and GSH levels. T(4) deiodination by the alternative pathways was significantly higher (P < 0.01) in G > P > F. In contrast both hepatic NP-SH and GSH concentrations were greater (P < 0.05) in P > F > G. The lack of a relationship between these parameters was further emphasized on analysis of tissue from rats fed G(c). Despite the clearcut (P < 0.01) increase in hepatic NP-SH and GSH consequent to G(c) feeding, there was no alteration in iodothyronine deiodination compared to the group fed glucose alone. These data indicate that the effects of diet on T(4) monodeiodination in liver are not mediated by changes in the tissue level of sulfhydryl compounds but rather involve alterations in the concentrations of the deiodinases.

Animals↗
PubMed1976

Mung bean nuclease I. Physical, chemical, and catalytic properties.

A simplified purification procedure for mung bean nuclease has been developed yielding a stable enzyme that is homogeneous in regards to shape and size. The nuclease is a glycoprotein consisting of 29% carbohydrate by weight. It has a molecular weight of 39 000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme contains 1 sulfhydryl group and 3 disulfide bonds per molecule. It has a high content (12.6 mol %) of aromatic residues. Approximately 70% of the enzyme molecules contain a peptide bond cleavage at a single region in the protein. The two polypeptides, 25 000 and 15 000 daltons, are covalently linked by a disulfide bond(s). Both the cleaved and intact forms of the enzyme are equally active in the hydrolysis of the phosphate ester linkages in either DNA, RNA, or adenosine 3'-monophophate. The enzymatic activity of mung bean nuclease can be stabilized at pH 5 in the presence of 0.1 mM zinc acetate, 1.0 mM cysteine, and 0.001% Triton X-100. The enzyme can be inactivated and reactivated by the removal and readdition of Zn2+ or sulfhydryl compounds.

Amino Acids↗
PubMed1991

Ferric iron absorption in rats: relationship to iron status, endogenous sulfhydryl and other redox components in the intestinal lumen.

Based on the hypothesis that Fe+3 must be reduced before Fe absorption, we investigated luminal factors that might participate in the physiological Fe+3 reduction. Rats were fed diets containing 7 mg Fe/kg diet [adequate iron (+Fe]) for 3 wk prior to a 10-min test of 59Fe absorption from an in vivo ligated duodenal segment. During absorption of 59Fe, the oxidation-reduction potential became more reducing and the pH rose in segment contents. There were small but significant differences between the -Fe and +Fe rats. In one experiment, the lumen environment was modified by bile duct ligation and/or intestinal perfusion prior to the absorption test. Ascorbic acid, nonprotein sulfhydryl compounds, Fe+2 and total ionizable Fe were measured in luminal contents. Nonprotein sulfhydryl concentration was positively correlated with, and the best predictor of, Fe absorption in -Fe rats.

Animals↗