Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Disulfides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1977

Identification of a coenzyme A--glutathione disulfide (DSI), a modified coenzyme A disulfide (DSII), and a NADPH-dependent coenzyme A--glutathione disulfide reductase in E. coli.

The nucleotides DSI and DSII induced during a slowdown in growth of E. coli have been characterized using chemical and biochemical analysis and by enzymic and alkaline fragmentation. DSI consists a coenzyme A and glutathione joined by a disulfide linkage. DSI could be isolated either containing Fe(III) with an A250:260 ratio of 1.05 or not containing iron with an A250:260 of 0.87. DSII (isolated in 10% the yield of DSI) is a coenzyme A disulfide dimer that also contains two molecules of glutamic acid. DSI was a substrate for NADPH-dependent CoAS-SG reductase (EC 1.6.4.6) which was present in crude extracts of E. coli. The specific activity of CoAS-SG reductase increased during growth from early log phase into stationary phase and during a shift from aerobic to anaerobic growth.

Coenzyme A↗
PubMed1978

Formation of interchain disulfide bonds in Bence Jones proteins and Fab(t) fragments of immunoglobulin G through thiol-disulfide interchange.

The formation of interchain disulfide bonds from partially reduced Bence Jones protein (Nag, type lambda) and Fab(t) fragments of IgG1 myeloma proteins was studied in the presence of various disulfide reagents. The results could be well explained in terms of the scheme proposed previously (Kishida et al. (1976) J. Biochem. 79, 91-105). In this scheme, it was assumed that two kinds of intermediate, which form mixed disulfides with either of the paired thiol groups, are produced. For type lambda Bence Jones proteins, only one of the two intermediates can form the inter L-L disulfide bond. The fraction of intermediate having the ability to form the inter L-L disulfide bond was estimated to be 72% of the total Nag protein and was the same irrespective of the kind of disulfide reagent examined. For Fab(t), on the other hand, both intermediates equally can form the inter Fd-L disulfide bond. On the basis of the results with cystamine, it was shown that the formation of an inter Fd-L disulfide bond from the intermediate proceeds about 100 times as rapidly as that of an inter L-L disulfide bond.

Bence Jones Protein↗
PubMed1977

Biologically oriented organic sulfur chemistry. 15. Organic disulfides and related substances. 41. Inhibition of the fungal pathogen Histoplasma capsulatum by some organic disulfides.

In an extension of promising inhibitory results in vitro against Histoplasma capsulatum, correlated earlier using substituent constants developed by regression analysis with 77 disulfides, one symmetrical and 14 unsymmetrical disulfides were prepared (3--17). About half were active in vitro against H. capsulatum (and one against Candida albicans). Groups that seemed most to lead to promising inhibition among the unsymmetrical disulfides were o-HO2CC6H4, (CH2)4SO2Na, Me2NC(S), p-ClC6H4, and perhaps p-CH3C6H4; the first two also might be used to increase solubility. Earlier inhibitory promise of the morpholino group did not materialize. None of the group 3--17 was significantly active in vivo. The unsymmetrical disulfides were prepared by reaction of thiols with sulfenyl chlorides or with acyclic or cyclic thiosulfonates. Two six-membered heterocyclic disulfides (5 and 6) were prepared by a novel cyclization, in which carbon disulfide reacted with an (N-alkylamino)ethyl Bunte salt, followed by ring closure; an explanation is suggested for formation of a thiazoline when the N-alkyl group is absent. One of the disulfides disproportionated with astonishing ease (31; 0.3--1 h at 25 degrees C).

Amphotericin B↗
PubMed1979

Disulfide-disulfide interchange catalyzed by a liver supernatant enzyme.

An enzyme widely distributed in rabbit tissues which catalyzes an interchange between N,N-di-dinitrophenyl-L-cystine and oxidized glutathione to form the mixed disulfide is described. D-Penicillamine disulfide can be substituted for oxidized glutathione and the mixed disulfide of cysteine and glutathione can serve as the sole substrate giving as one product of interchange, oxidized glutathione. The enzyme is very labile and only limited purification of it has been achieved. The activity increases with increasing pH above 6.6, the Km for N,N-di-dinitrophenyl-L-cystine is 0.2 mM and for oxidized glutathione 0.8 mM. The enzyme is inhibited by SH reagents with protection against iodoacetamide inactivation provided by N,N-di-dinitrophenyl-L-cystine. Evidence is presented that disulfide-disulfide interchange enzyme is a different activity from the previously described protein disulfide isomerase and thiol transferase.

Animals↗
PubMed1976

Enzyme reduction of disulfide bonds by thioredoxin. The reactivity of disulfide bonds in human choriogonadotropin and its subunits.

The NADPH-dependent enzymic reduction of disulfide bonds in human choriogonadotropin and its two subunits, alpha and beta, was examined with thioredoxin and thioredoxin reductase from Escherichia coli. With 12 muM thioredoxin and 0.1 muM thioredoxin reductase at pH 7 all disulfide bonds in the alpha subunit could be reduced in 15 min. The reduction of disulfide bonds was recorded by a simple spectrophotometric assay at 340 nm, which allowed quantitation of the reduction rate and the number of disulfide bonds reduced. Partial reduction of the alpha subunit with thioredoxin followed by S-carboxymethylation with iodol[2-3H]acetic acid and analysis of tryptic peptides indicated that all S-S bonds in the alpha subunit were surface oriented and equally reactive. The usefulness of thioredoxin reduction of disulfide bonds as a chemical probe of protein structure was shown by the much slower reaction of disulfide bonds in the intact hormone as compared to its two biologically inactive subunits.

Aerobiosis↗
PubMed1976

Enzymic and immunochemical properties of lysozyme. XIII. Accurate delineation of the reactive site around the disulfide 6-127 by immunochemical study of beta-propiolactone lysozyme derivative and of synthetic disulfide peptides.

In previous reports from this laboratory it was shown that an antigenic reactive site resides around the sequences 6-13 and 126-128 linked by the disulfide 6-127. The present work provides a strong support for the location of the reactive site by an independent approach. It also determines accurately the boundaries of the reactive site. 1. The two methionine residues in lysozyme were carboxyethylated by reaction with beta-propiolactone. The electrophoretically homogeneous derivative had no other modified amino acids and showed no conformational changes, relative to native lysozyme, as determined by ORD and CD measurements. However, it exhibited a slight increase in disulfide reducibility relative to native lysozyme and its lytic activity was about half that of native lysozyme, probably as a result of the slight conformational change. On the other hand, the antigenic reactivity of the derivative was equal to that of native lysozyme with several goat and rabbit antisera to lysozyem. It was therefore concluded that methionines 12 and 105 were not parts of antigenic reactive sites in native lysozyme. 2. Eleven peptides, corresponding to various sequences on the two sides of the disulfide 6-127 (i.e. two groups of peptides) were synthesized, purified and characterized. One group (A) of peptides comprised sequences 3-14, 5-14, 6-14, 5-13, 5-12 and an analog of sequence 5-14 in which methionine 12 is replaced by glycine. The second group (B) of peptides comprised sequences 125-129, 125-128, 126-128, 127-128, and 125-127. From groups A and B, nine disulfide-containing peptides (see Fig. 2) were synthesized, purified, characterized and their immunochemical interactions with antisera to native lysozyme studied. Towards each of the antisera studied here, Phe-3, Gly-4, Arg-5, Arg-125 and Leu-129 were not essential parts of the reactive site. On the other hand, Arg-14, Lys-13, Gly-126 and with some antisera Arg-128 were each critical for the reactivity of the site. Peptides from group A alone or group B alone did not inhibit the reaction of lysozyme with its antisera, confirming our previous findings that the integrity of the disulfide bond is essential for bringing the two distant (in sequence) parts of the site together. Finally, replacement of Met-12 by glycine did not influence the immunochemical reactivity of the site, confirming the above conclusion that neither of the two methionine residues takes part in interaction of lysozyme with its antibodies. An accurate delineation of the antigenic reactive site is, therefore derived here and its shape in the three-dimensional structure of native lysozyme is described.

Amino Acid Sequence↗
PubMed1977

Formation of the four isomers of hen egg white lysozyme containing three negative disulfide bonds and one open disulfide bond.

Reduced partially carboxymethylated hen egg white lysozyme (mucopeptide N-acetylmuramoylhydrolase; EC 3.2.1.17) (approximately 0.8 mol of [1-(14)C]carboxymethyl groups) was air oxidized at pH 8.0 and 37 degrees in the presence of 1.5 mM 2-mercaptoethanol for 36 hr. Gel filtration of this product gave the lower (native) and higher hydrodynamic volume forms, both containing radioactivity (approximately 35 and 65%, respectively). Ion exchange chromatography of the lower hydrodynamic volume forms yielded renatured lysozyme, two major radioactive samples (LH(C) and LH(D)) eluting at the positions of monocarboxymethylated lysozyme, and two minor radioactive samples eluting at the positions of dicarboxymethylated lysozyme. Sample LH(C) (approximately 23% of the radioactivity) was essentially homogeneous with respect to electrophoretic mobility, exhibited approximately 39% of the enzymic activity of lysozyme, and contained 0.95 mol of [(14)C]carboxymethyl groups. Sample LH(D) (approximately 8% of the radioactivity) was also enzymically active and contained approximately 0.5 mol of [(14)C]carboxymethyl groups; this low value is apparently due to contamination of noncarboxymethylated species. The radioactive tryptic peptides from samples LH(C) and LH(D) were characterized. The results indicated that all eight isomers, containing three presumably native disulfide bonds and one free and one carboxymethylated sulfhydryl group, are formed on air oxidation of reduced partially carboxymethylated lysozyme. Since in each of these isomers the formation of one of the four native disulfide bonds is permanently blocked, it would follow that no one of the four disulfide bonds of native lysozyme is obligatory in the formation of the other three native disulfide bonds.

Amino Acid Sequence↗
PubMed1979

Identification of an NADH-linked disulfide reductase from Bacillus megaterium specific for disulfides containing pantethine 4',4''-diphosphate moieties.

Bacillus megaterium contains an NADH-linked disulfide reductase that is specific for disulfides containing pantethine 4',4''-diphosphate moieties. This reductase is at its highest level in cells late in sporulation and in dormant spores, and could be involved in the formation and cleavage of coenzyme A-protein disulfides which take place late in sporulation and early in spore germination, respectively.

Bacillus megaterium↗
PubMed1976

Disulfide bond-modified trypsinogen. Role of disulfide 179-203 on the specificity characteristics of bovine trypsin toward synthetic substrates.

Disulfide 179-203 of trypsinogen was cleaved and the free sulfhydryls were modified by S-carboxymethylation, S-carboxyamidomethylation, or by S-aminoethylation. The enzymatic properties of the activated, modified zymogens toward specific and nonspecific trypsin substrates were studies. The three S-alkylated trypsins hydrolyzed N-benzoylarginine ethyl ester and N-tosyl-lysine methyl ester with Kcat values similar to those of trypsin but with Km values that were increased by 2 to 3 orders of magnitude. The binding constant of the competitive inhibitor benzamidine to the S-alkylated trypsins was increased by 2 orders of magnitude by the modifications. The association constant of soybean trypsin inhibitor with S-carboxyamidomethyl trypsin was several orders of magnitude less than normal. Hydrolysis of benzoyl arginine amide with S-carboxymethyl trypsin was not detected, but this was ascribed to poor binding since a KI of 0.3 M was estimated from competitive inhibition studies. The altered kinetics did not depend on the type of chemical group used for the S-alkylated derivative, nor were the kinetics of any derivative significantly influenced by changes of pH or ionic strength. Nonspecific substrates, such as acetylglycine p-nitrophenyl ester and p-nitrophenylacetate, were hydrolyzed at equal rates by both trypsin and disulfide-modified trypsins, and both substrates had identical kcat/Km ratios with unmodified trypsins. For S-alkylated trypsins, kcat/km with lysine and arginine substrates were lower than normal and were the same order of magnitude as the values found for nonspecific substrates, suggesting normal catalytic behavior but a loss of specificity in binding substrates. The kinetic evidence suggested that the role of disulfide 179-203 in the mechanism of action of trypsin is to maintain the geometry of the specificity pocket by keeping appropriate residues of the pocket in a rigid framework.

Animals↗
PubMed1977

Carbon disulfide. I. The metabolism of inhaled carbon disulfide in the rat.

The pharmacokinetics of inhaled carbon disulfide (CS2) vapor was evaluated in rats. Estimates of free CS2 and its nonvolatile, acid-labile metabolites (AL CS2) were made in a variety of rat tissues after an 8-hour inhalation exposure to CS2 vapor (2 mg/l of air). At the end of the exposure, all tissues examined contained appreciable amounts of the native solvent and AL CS2. Elimination of CS2 from the rat during the postexposure period was rapid and occurred primarily via the lungs. Excretion of AL CL2 occurred primarily via the kidneys and was prolonged with respect to that of free CS2. Accumulation of these metabolites upon repeated exposures and their presence in all tissues examined suggest that they may play a role in the toxicity of CS2.

Animals↗
PubMed1977

[Effect of carbon disulfide on peripheral blood leukocytes. I. Effect of carbon disulfide on in vitro chromosome structure and division capability of leukocytes in man].

The peripheral blood leukocytes in normal subjects were cultured according to Moorhead with addition of CS2 (0,75 microliter/ml of culture). It has been found that CS2 decreases the mitotic index, and in some cultures inhibits totally the cell division. Moreover, it causes structural disturbances of chromosomes being of pre- and postreplicative character as well as their viscous degeneration, lesser spiralization and sometimes pulverization. The presence of greater amount of erythrocytes of the donor's blood in the culture markedly diminished the intensity of these changes.

Adolescent↗
PubMed1977

Partial reduction with dithiothreitol of disulfide bonds in human chorionic gonadotropin.

Of the eleven disulfide bonds of human chorionic gonadotropin (hCG), two were reduced with a 10-fold molar excess of dithiothreitol (DTT) relative to hormone. An S-carboxymethyl (SCM) derivative and a reoxidized product of this reduced hCG retained full biologic activity and were likely to be immunologically identical with native hCG. These two disulfide bonds appeared to be located in the alpha-subunit of the hormone. A 40-fold molar excess of DTT was required to reduce the third disulfide bond which was located in the beta-subunit. An SCM derivative ot this hexa-SH-hCG was only one fifth as biologically active as native hCG but its immunologic activity was only slightly decreased. However, its reoxidized product exhibited over 70% of the biologic activity of and it had nearly the same immunologic activity as the hormone. Reduction of a fourth disulfide bond, probably in the beta-subunit, by a 100-fold molar excess of the reagent was accompanied by considerable alterations in the hormone conformation as evidenced by electrophoresis. The resulting SCM derivatives as well as reoxidized products showed progressive decreases in biologic and immunologic activity and both reduced deca-SCM-hCG and a reoxidized product of deca-SH-hCG were virtually devoid of biologic activity. These findings suggest that the two first-reduced disulfide bonds, apparently in the alpha-subunit, are not important to the biologic activity of the hormone and that the third-reduced disulfide bond, probably in the beta-subunit, is very important in maintaining a biologically active conformation of the hormone. Further disulfide reduction appears to result in considerable alterations in the general conformation of the hormone, including disulfide interchange.

Binding Sites↗
PubMed1976

Formation of interchain disulfide bonds in Bence Jones proteins and immunoglobulins.

The formation of the interchain disulfide bonds in partially reduced Bence Jones proteins and immunoglobulins was studied in the presence of glutathione. It was found that only oxidized glutathione (GSSG) was effective for the formation of the interchain disulfide bonds in type gamma Bence Jones proteins and IgG. In type kappa Bence Jones proteins, on the other hand, no formation of the inter L-L disulfide bond was observed in the presence of GSSG at above pH 6. The kinetic pattern of disulfide bond formation of Bence Jones proteins was well interpreted by assuming that two monomers of a type gamma protein dimer are discriminated (monomers 1 and 2) and that only an intermediate in which the SH group on monomer 1 is blocked with GSSG can form a disulfide-bonded dimer and the intermediate in which the SH group on monomer 2 is blocked with GSSG can not. Comparison of the kinetic data for the formation of the interchain disulfide bonds of IgG with those for Bence Jones proteins suggested that H chain-GSSG mixed disulfide is a principal intermediate for the formation of the inter H-L disulfide bond.

Bence Jones Protein↗