Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cysteine”

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 235 records · Page 13Linked to original sources
PubMed2001

Role of the single cysteine residue, Cys 3, of human and bovine cystatin B (stefin B) in the inhibition of cysteine proteinases.

Cystatin B is unique among cysteine proteinase inhibitors of the cystatin superfamily in having a free Cys in the N-terminal segment of the proteinase binding region. The importance of this residue for inhibition of target proteinases was assessed by studies of the affinity and kinetics of interaction of human and bovine wild-type cystatin B and the Cys 3-to-Ser mutants of the inhibitors with papain and cathepsins L, H, and B. The wild-type forms from the two species had about the same affinity for each proteinase, binding tightly to papain and cathepsin L and more weakly to cathepsins H and B. In general, these affinities were appreciably higher than those reported earlier, perhaps because of irreversible oxidation of Cys 3 in previous work. The Cys-to-Ser mutation resulted in weaker binding of cystatin B to all four proteinases examined, the effect varying with both the proteinase and the species variant of the inhibitor. The affinities of the human inhibitor for papain and cathepsin H were decreased by threefold to fourfold and that for cathepsin B by approximately 20-fold, whereas the reductions in the affinities of the bovine inhibitor for papain and cathepsins H and B were approximately 14-fold, approximately 10-fold and approximately 300-fold, respectively. The decreases in affinity for cathepsin L could not be properly quantified but were greater than threefold. Increased dissociation rate constants were responsible for the weaker binding of both mutants to papain. By contrast, the reduced affinities for cathepsins H and B were due to decreased association rate constants. Cys 3 of both human and bovine cystatin B is thus of appreciable importance for inhibition of cysteine proteinases, in particular cathepsin B.

Animals↗
PubMed1996

Substitution of cysteine 192 in a highly conserved Streptococcus pyogenes extracellular cysteine protease (interleukin 1beta convertase) alters proteolytic activity and ablates zymogen processing.

Virtually all strains of the human pathogenic bacterium Streptococcus pyogenes express a highly conserved extracellular cysteine protease. The protein is made as an inactive zymogen of 40,000 Da and undergoes autocatalytic truncation to result in a 28,000-Da active protease. Numerous independent lines of investigation suggest that this enzyme participates in one or more phases of host-parasite interaction, such as inflammation and soft tissue invasion. Replacement of the single cysteine residue (C-192) with serine (C192S mutation) resulted in loss of detectable proteolytic activity against bovine casein, human fibronectin, and the low-molecular-weight synthetic substrate 7-amino-4-trifluoromethyl coumarin. The C192S mutant molecule does not undergo autocatalytic processing of zymogen to mature form. Taken together, these data support the hypothesis that C-192 participates in active-site formation and enzyme catalysis.

Animals↗
PubMed2004

Pro domain peptide of HGCP-Iv cysteine proteinase inhibits nematode cysteine proteinases.

Cysteine proteinases (CPs) are synthesized as zymogens and converted to mature proteinase forms by proteolytic cleavage and release of their pro domain peptides. A cDNA encoding a papain-like CP, called hgcp-Iv, was isolated from a Heterodera glycines J2 cDNA library, expressed and utilized to assess the ability of its propeptide to inhibit proteinase in its active form. The hgcp-Iv cDNA sequence encodes a polypeptide of 374 amino acids with the same domain organization as other cathepsin L-like CPs, including a hydrophobic signal sequence and a pro domain region. HGCP-Iv, produced in Escherichia coli as a fusion protein with thioredoxin, degrades the synthetic peptide benzyloxycarbonyl-Phe-Arg-7-amido-4-methylcoumarin and is inhibited by E-64, a substrate and inhibitor commonly used for functional characterization of CPs. Recombinant propeptides of HGCP-Iv, expressed in E. coli, presented high inhibitory activity in vitro towards its cognate enzyme and proteinase activity of Meloidogyne incognita females, suggesting its usefulness in inhibiting nematode CPs in biological systems. Cysteine proteinases from other species produced no noticeable activity.

Amino Acid Sequence↗
PubMed1998

Cysteine proteases and cysteine protease inhibitors in non-small cell lung cancer.

In this study we investigated the levels of two lysosomal cysteine protease proteins cathepsin B (CB) and cathepsin L (CL) and the levels of three cysteine protease inhibitor proteins stefin A (SFA), stefin B (SFB) and cystatin C (CNC) in squamous-cell lung carcinoma (SQCLC) and matched lung parenchyma specimens and examined the inhibition of CB and cathepsin C (CC) activities by endogenous inhibitors in extracts from SQCLC, lung adenocarcinoma (LAC) and lung parenchyma specimens. We found that Stage I SQCLCs contained significantly increased levels of CB protein, CB activity and SFA protein as compared to matched lungs. Neither the levels of CL protein nor the levels of SFB protein nor the levels of CNC protein in Stage I SQCLCs and the lungs were significantly different, but the levels of CB and CL proteins as well as the levels of SFA and SFB proteins showed significant positive correlation in SQCLCs. In SQCLCs as well as in the lungs the level of SFB protein was significantly higher than the level of SFA protein or the level of CNC protein. In the lungs the levels of SFA protein and CNC protein revealed a weak negative correlation trend. In extracts from SQCLCs the level of SFA protein showed a weak negative correlation with the residual CB activity (i.e. the activity remaining after extract preincubation) whereas in extracts from the lungs the level of CNC protein displayed a weak negative correlation trend with the residual CB activity and with the residual CC activity. We observed that SQCLCs and LACs contained not only a significantly increased activity of CB but also a significantly higher inhibitory potential against the activity of endogenous CB as compared to matched lungs. Leupeptin, a small inhibitor of CB, was capable to protect CB in lung carcinoma and lung parenchyma extracts from preincubation-induced inhibition, revealing an active-site directed and competitive nature of CB inhibition by endogenous cystatins. Ultrafiltration passaged protein preparations of nominal Mr < or = 30,000 obtained from extracts of SQCLCs inhibited significantly higher quantities of activity of purified bovine spleen CC than did such protein preparations from matched lungs. Reaction courses of purified bovine spleen CC that had been preincubated with such protein preparations resembled those of endogenous CC from SQCLC and lung extracts showing a slow steady-state approach. These observations and the relaxation kinetics of CC from SQCLC and lung extracts suggest that CC in the extracts may be complexed with some cystatins. In conclusion, our results indicate that quantitatively different combinations of cystatins are the major constituents of the inhibitory potential against CB and CC in SQCLCs and the lungs.

Adenocarcinoma↗
PubMed1990

Syntheses of metabolites of S-carboxymethyl-L-cysteine and S-methyl-L-cysteine and of some isotopically labelled (2H, 13C) analogues.

The chemical syntheses of human metabolites of S-carboxymethyl-L-cysteine (3) and S-methyl-L-cysteine (12) are described. The additional preparation of some 2H- and 13C-labelled isotopomers enabled the direct evaluation of the stabilities of 3 and 12 under physiological conditions and also facilitated the unambiguous assignments of the signals in the 13C-NMR spectra of all compounds mentioned.

Carbocysteine↗
PubMed2006

Separation and quantification of N-acetyl-l-cysteine and N-acetyl-cysteine-amide by HPLC with fluorescence detection.

N-acetyl-l-cysteine (NAC) is a well-known antioxidant that is capable of facilitating glutathione (GSH) biosynthesis and replenishing intracellular GSH under oxidatively challenging circumstances. N-acetyl-cysteine-amide (NACA), the amide form of NAC, is a newly designed and synthesized thiol-containing compound which is believed to be more lipophilic and permeable through cell membranes than NAC. The metabolic and antioxidant effects of these compounds in vitro and in vivo are under investigation. However, an analytical method that can separate and quantify both compounds simultaneously is not yet available, to the best of our knowledge. Because of their structural similarities, the two compounds are difficult to separate using earlier HPLC methods which were designed for NAC quantification. Therefore, the goal of this work was to develop an HPLC method with fluorescence detection for simultaneous quantification of NAC and NACA in biological blood and tissue samples. A gradient HPLC program with fluorescence detection (lambda(ex) = 330 nm, lambda(em) = 376 nm) using N-(1-pyrenyl)maleimide (NPM) as the derivatizing agent was developed. The calibration curves were linear over a concentration range of 25-5000 nm (r(2) > 0.997). The coefficients of variation for within-run precision and between-run precision ranged from 0.67 to 5.23% and for accuracy ranged from 0.98 to 10.54%; the percentage relative recovery ranged from 94.5 to 102.8%. This new method provides satisfactory separation of NAC and NACA, along with other biological thiols, in 20 min with a 5 nm limit of detection (LOD) per 5 microL injection volume.

Acetylcysteine↗
PubMed2005

Further studies on the fragmentation of protonated ions of peptides containing aspartic acid, glutamic acid, cysteine sulfinic acid, and cysteine sulfonic acid.

Here we examined the fragmentation, on a quadrupole ion-trap mass spectrometer, of the protonated ions of a group of peptides containing one arginine and two different acidic amino acids, one being aspartic acid (Asp) or glutamic acid (Glu) and the other being cysteine sulfinic acid [C(SO2H)] or cysteine sulfonic acid [C(SO3H)]. Our results showed that, upon collisional activation, the cleavage of the peptide bond C-terminal to C(SO2H) is much more facile than that of the peptide bond C-terminal to Asp, Glu, or C(SO3H). There is no significant difference, however, in susceptibility to cleavage of peptide bonds that are C-terminal to Asp, Glu, and C(SO3H). To understand these experimental observations, we carried out B3LYP/6-31G* density functional theory calculations for a model cleavage reaction of GXG --> b2 + Gly, in which X is Asp, Glu, C(SO2H), or C(SO3H). Our calculation results showed that the cleavage reaction is thermodynamically more favorable when X = C(SO2H) than when X = Asp or C(SO3H). We attributed the less facile cleavage of the amide bond after Glu to that the formation of a six-membered ring b ion for Glu-bearing peptides is kinetically not as favorable as the formation of a five-membered ring b ion for peptides containing the other three acidic amino acids. The results from this study may provide useful tools for peptide sequencing.

Amino Acid Sequence↗
PubMed2001

Determination of reduced, protein-unbound, and total concentrations of N-acetyl-L-cysteine and L-cysteine in rat plasma by postcolumn ligand substitution high-performance liquid chromatography.

A high-performance liquid chromatographic assay was developed for the quantitative determination of the sulfur-containing amino acids N-acetyl-L-cysteine (NAC) and L-cysteine (Cys) in rat plasma. The thiols were separated by reverse-phase ion-pair chromatography, and the column eluent was continuously mixed with an iodoplatinate-containing solution. The substitution of sulfur of the thiol compound with iodide was quantitatively determined by measuring changes in the absorption at 500 nm. The low-molecular-weight disulfides and mixed disulfide conjugates of thiols with proteins were entirely reduced to the original reduced compounds by dithiothreitol. By reducing these two types of disulfides separately during sample pretreatment, the reduced, protein-unbound, and total thiol concentrations could also be determined. Validation testing was performed, and no problems were encountered. The limit of detection was approximately 20 pmol of thiol on the column. The present method was used to measure the plasma concentrations of NAC and Cys in the rat after a bolus intravenous administration of NAC, focusing on disulfide formation. The binding of NAC to protein through mixed disulfide formation proceeds in a time-dependent and reversible manner. Moreover, this "stable" covalent binding might limit total drug elimination, while the unbound NAC is rapidly eliminated. Consequently, the analytical method described in this study is very useful for the determination of plasma NAC and Cys, including disulfide conjugates derived from them.

Acetylcysteine↗
PubMed1997

Disulfide bond formation of cysteine-37 and cysteine-66 of beta B2 crystallin during cataractogenesis of the human lens.

Beta B2 crystallin has been prepared from total protein of normal (transparent) and cataractous human lenses. After digestion with endoprotease lys-C, the crude digests were resolved on a C18 reverse phase column. The lys-C digests of beta B2 crystallin from cataractous lenses consistently showed the presence of a major peptide that was not present in the lys-C digests from normal lenses. Treatment of this peptide with dithiothreitol resulted in the production of two peptides, corresponding to beta B2 crystallin sequences 18-41 and 48-67, containing cysteine-37 and cysteine-66, respectively. The results demonstrated that intramolecular disulfide bonding of these two residues had occurred in vivo. Based upon previous knowledge of the three dimensional structure of beta B2 crystallin, formation of this disulfide bond suggests that significant denaturation of the beta B2 crystallin molecule has occurred during the process of human lens opacification.

Aged↗
PubMed1976

[Thermal decomposition of cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid and cysteine methyl ester in soy bean oil (authors transl)].

During the thermal decomposition of cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid, cysteine methyl ester, in soy bean oil at 200 degrees C, a series of compounds containing sulphur are formed. Besides 15 alkylthiazoles, -thiazolines and -thiazolidines, compounds with 2 and 3 S-atoms can also be identified: ethane-1,2-dithiole, diethyldisulfide, diethyltrisulfide, 2-methyl-1,3-dithiolane, 1,2-dithiane, thialdine, 1,2,4-trithiolanes, 1,2,4-trithianes and 2-methyl-thiazolidino-(3,4-b-)-thiazolidine. N,N'-dibutyrylcystamine shows an antioxidant effect.

Acetylcysteine↗
PubMed1996

Alterations of the renal function in the isolated perfused rat kidney system after in vivo and in vitro application of S-(1,2-dichlorovinyl)-L-cysteine and S-(2,2-dichlorovinyl)-L-cysteine.

The nephrotoxic effects of the two isomers S-(1,2-dichlorovinyl)-L-cysteine (1,2-DCVC) and S-(2,2-dichlorovinyl)-L-cysteine (2,2-DCVC) were investigated comparatively in the isolated perfused rat kidney with two different treatment regimens. In the first approach, the kidneys were exposed to the test compounds dissolved in the perfusion media after removal from the animal. In the second approach the test compounds were administered to rats in vivo and the nephrotoxicity was assessed in the isolated perfused kidney 6 h and 18 h post-treatment. The vicinal isomer 1,2-DCVC produced concentration- and time-dependent nephrotoxicity with both treatment regimens, as indicated by the impairment of glucose reabsorption, the increase of protein excretion and of gamma-glutamyltransferase and alkaline phosphatase activities in urine. In contrast to the marked toxicity observed after in vivo and in vitro administration of 1,2-DCVC, the geminal isomer, 2,2-DCVC, was not nephrotoxic at all concentrations (0.5 and 2.5 mM in vitro, 40 and 70 mg/kg in vivo) investigated.

Animals↗
PubMed2002

Immunolocalization of cysteine proteinases (cathepsins) and cysteine proteinase inhibitors (salarin and salmon kininogen) in Atlantic salmon, Salmo salar.

Tissue localization of cysteine proteinases (cathepsins) and their inhibitors (salarin, salmon kininogen) was performed in tissues of the Atlantic salmon. In skin, both epidermis and dermis were strongly stained by antisera against salarin and salmon kininogen. In epidermis the intercellular space seemed to be heavily stained (salarin). In kidney, the inhibitors were mainly localized to the interstitial capillaries. Also, some epithelial cells of the tubules (salarin) and some cells of the interstitium were stained. Mostly, the staining had a diffuse cytoplasmic localization. In the liver some hepatocytes were strongly positive for salarin and salmon kininogen. Purified fish cysteine proteinase inhibitors were not found to inhibit the growth of fish pathogenic bacteria and viruses. In the trunk kidney cathepsins B and L were localized in epithelial cells of the tubules (proximal part) and in cells of the interstitium. Mostly, the staining showed a prominent lysosomal localization. In head kidney large macrophage-like cells were positively stained for cathepsin B. The staining was localized to granula/vacuoles in the cytoplasm. In the liver, some hepatocytes were strongly stained and some were less strongly positive for cathepsin B and L. Mostly, the hepatocytes showed lysosomal staining. Cathepsin L was found in some big macrophage-like cells in the spleen. Mucosal epithelial cells of the esophagus and intestine seemed to be strongly stained for cathepsin B and L. The results show that cathepsins and their inhibitors are specifically and widely distributed in the Atlantic salmon skin indicating that they perform some biologically important and specific but so far unknown functions.

Animals↗
PubMed1991

High-performance liquid chromatography of thiazolidinic compounds obtained by condensation of pyridoxal 5'-phosphate or pyridoxal with aminothiols (L- or D-cysteine, cysteamine, L-cysteine ethyl ester).

We investigated six thiazolidine 4-carboxylic acids of biological interest, obtained by condensation of pyridoxal 5'-phosphate or pyridoxal with L- or D-cysteine, cysteamine or L-cysteine ethyl ester. A reversed-phase high-performance liquid chromatographic method, using a C18 column for their separation, was developed by sequential optimization of the pH and the gradient of the mobile phase. Resolution of the compounds was obtained with an analysis time of less than 20 min.

Chromatography, High Pressure Liquid↗
PubMed1989

N-acetyl S-(1,2-dichlorovinyl)-L-cysteine produces a similar toxicity to S-(1,2-dichlorovinyl)-L-cysteine in rabbit renal slices: differential transport and metabolism.

Renal cortical slices were used to determine the toxicity of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (N-acetyl-DCVC) as well as to investigate the transport and metabolism of S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and the N-acetyl derivative. N-Acetyl-DCVC produced dose- and time-dependent decreases in intracellular K+ content and lactate dehydrogenase activity. Histopathology demonstrated an initial S3 lesion followed by a lesion inclusive of all proximal tubules. N-Acetyl-DCVC was shown to be transported via the organic anion system by its ability to inhibit PAH transport by the cells and the ability of probenecid to decrease uptake (80%) and toxicity of N-acetyl-DCVC. DCVC, in contrast, was not transported by the organic anion system, but may be transported by one or more amino acid systems. N-Acetyl-DCVC must be deacetylated before undergoing metabolism by beta-lyase. This process must occur since covalent binding of a 35S-labeled reactive product from N-acetyl [35S]DCVC is observed within 1 hr. Both the uptake inhibitor, probenecid, and aminooxyacetic acid (AOAA), a beta-lyase inhibitor, decreased the covalent binding from N-acetyl [35S]DCVC (80 and 50%, respectively), but only AOAA inhibited the covalent binding of DCVC. AOAA also partially inhibited the toxicity of DCVC and N-acetyl-DCVC as determined by intracellular K+ content, lactate dehydrogenase activity, and histopathology. Despite the fact that a separate transport system and an additional enzymatic step (deacetylation) are required, N-acetyl-DCVC produces a lesion with similar intratubular specificity to that seen with DCVC. Therefore, the S3 specificity seen in vivo could be produced by either compound.

Acetylation↗
PubMed1996

Effects of age on levels of cysteine, glutathione and related enzyme activities in livers of mice and rats and an attempt to replenish hepatic glutathione level of mouse with cysteine derivatives.

There was a large statistically significant decrease in the hepatic level of cysteine and glutathione (GSH) in 24 month-old mice compared to young mice, while, cystine and glutathione disulfide (GSSG) contents in the liver did not differ between young and old mice. Activities of cystathionine gamma-lyase and beta-synthase in mouse liver of the 24 month-old group were significantly decreased. In rats, the hepatic levels of cysteine, cystine, GSH and GSSG exhibited no statistically significant change during aging to 30 month. As the rats matured, total hepatic activities of both cystathionine gamma-lyase and beta-synthase increased with maximum levels at 24 months of age and decreased to the same level found in 5 week old for the former and to 22% of that in 5 week old for the latter. Intraperitoneal administration of diethyl maleate to mice led to depletion of hepatic GSH. When N-acetylcysteine and a thiazolidine derivative were intravenously injected after diethyl maleate administration, the hepatic GSH level of mice was restored to the normal level.

Acetylcysteine↗
PubMed1989

Cysteine-22 and cysteine-38 are not essential for the functions of maltoporin (LamB protein).

Maltoporin in the outer membrane of Escherichia coli contains two cysteine residues, at positions 22 and 38 in the primary sequence. The role of these residues in determining structural stability, and their contributions to the maltoporin binding sites for maltodextrins and bacteriophage lambda, was investigated. Site-directed mutagenesis was used to alter each of these residues to a serine. A double mutant lacking both cysteines was also isolated. None of the substitutions affected maltodextrin binding or the binding of phage lambda, suggesting the variant proteins retain a native binding-site conformation. The mutants were assembled at wild-type levels into the outer membrane as maltoporin trimers but the temperature-stability of the trimer greater than monomer dissociation was slightly reduced in the presence of the Cys 38 substitution. However, it is unlikely that the stability of trimers was due to disulfide linkages between subunits since the native trimers are stable under highly reducing conditions in the presence of SDS; more likely the Cys greater than Ser substitutions slightly perturb intra- or inter-subunit hydrophobic interactions in regions predicted to span across the outer membrane.

Bacterial Outer Membrane Proteins↗
PubMed1995

Preparation and biological behaviour of 99mTc-carbonyl and 99mTc-nitrido complexes of cysteine and some cysteine esters.

The preparation of 99mTcO-, 99mTcN- and 99mTc(CO)-complexes of cysteamine (CYA), cysteine (CYS) and the methyl (CME) and ethyl (CEE) esters of cysteine is described. All complexes were stable and their biological behaviour in mice was studied. Most complexes were found to clear predominantly via the renal pathway with TcN- and Tc(CO)-complexes exhibiting greater urinary clearance than the corresponding TcO-complex. 99mTcN-CME, 99mTc(CO)-CME and 99mTc(CO)-CYS were found to be rapidly cleared via the kidneys and the effect of probenicid on renal clearance was studied to determine whether tubular excretion was involved. The results suggest that tubular secretion is involved in the renal clearance of 99mTcN-CME and Tc(CO)-CYS.

Animals↗