Thiol-blocking reagents and phosphate acetyltransferase catalysis, and the assessment of protection by adsorbed molecules.
Ontology highlight
ABSTRACT:
SUBMITTER: Kyrtopoulos SA
PROVIDER: S-EPMC1168195 | biostudies-other | 1974 Sep
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Se-Aryl selenenylthiosulphates and S-aryl sulphenylthiosulphates inhibit papain at pH 5.8 much more rapidly than do the corresponding Se-aryl selenosulphates and S-aryl thiosulphates, and also more rapidly than do Se-alkyl selenosulphates. Se-p-Nitrophenyl selenenylthiosulphate and S-p-nitrophenyl sulphenylthiosulphate inactivate papain most rapidly, but the inactivation is slowly and spontaneously reversible. Inactivation by Se-o-nitrophenyl selenenylthiosulphate and S-o-nitrophenyl sulphenylthiosulphate, although less rapid than that by the para isomers, is essentially irreversible.
| S-EPMC1144109 | biostudies-other
Project description:Potassium benzyl selenosulphate and potassium p-nitrobenzyl selenosulphate were shown to be powerful inhibitors of the thiol-dependent enzymes glutathione reductase and papain, but to have no effect on the serine-dependent proteinase trypsin. By contrast, potassium benzyl thiosulphate and potassium p-nitrobenzyl thiosulphate, at much higher concentrations, have virtually no effect on any of the enzymes. The selenosulphates show characteristics of both reversible non-competitive and irreversible inhibition. On the basis of model reactions in which the selenosulphates react instantly with cysteine, it is suggested that they form labile selenosulphide derivatives with the enzymes, but that these derivatives may be broken down either by the normal functioning of the enzyme (in the case of glutathione reductase) or by the approaching substrate (in the case of papain). Continued inhibition of the enzymes requires a stoicheiometric excess of inhibitor over enzyme.
| S-EPMC1163644 | biostudies-other
Project description:The kinetics of the reaction of d-glyceraldehyde 3-phosphate dehydrogenase with 5,5'-dithiobis-(2-nitrobenzoic acid) show that NAD(+) dissociates from the enzyme before the reaction. In contrast 2-chloromercuri-4-nitrophenol reacts with the holoenzyme without prior dissociation of NAD(+). These studies and observations on the dissociation constant of NAD(+) to the lobster enzyme show that NAD(+) must dissociate from sites modified by substrates during the reductive dephosphorylation of 1,3-diphosphoglycerate. All four sites per tetramer of the apoenzyme are acylated by 1,3-diphosphoglycerate. Hydrolysis of the acyl-enzyme occurs at a significant rate even in the absence of NAD(+), which may explain previous estimates that only two sites per tetramer can readily be acylated.
| S-EPMC1177227 | biostudies-other
Project description:Gcn5 serves as the defining member of the Gcn5-related N-acetyltransferase (GNAT) superfamily of proteins that display a common structural fold and catalytic mechanism involving the transfer of the acyl-group, primarily acetyl-, from CoA to an acceptor nucleophile. In the case of Gcn5, the target is the ε-amino group of lysine primarily on histones. Over the years, studies on Gcn5 structure-function have often formed the basis by which we understand the complex activities and regulation of the entire protein acetyltransferase family. It is now appreciated that protein acetylation occurs on thousands of proteins and can reversibly regulate the function of many cellular processes. In this review, we provide an overview of our fundamental understanding of catalysis, regulation of activity and substrate selection, and inhibitor development for this archetypal acetyltransferase.
| S-EPMC7854473 | biostudies-literature
Project description:The basis for a quantum-mechanical description of matter is electron wave functions. For atoms and molecules, their spatial distributions and phases are known as orbitals. Although orbitals are very powerful concepts, experimentally only the electron densities and -energy levels are directly observable. Regardless whether orbitals are observed in real space with scanning probe experiments, or in reciprocal space by photoemission, the phase information of the orbital is lost. Here, we show that the experimental momentum maps of angle-resolved photoemission from molecular orbitals can be transformed to real-space orbitals via an iterative procedure which also retrieves the lost phase information. This is demonstrated with images obtained of a number of orbitals of the molecules pentacene (C22H14) and perylene-3,4,9,10-tetracarboxylic dianhydride (C24H8O6), adsorbed on silver, which are in excellent agreement with ab initio calculations. The procedure requires no a priori knowledge of the orbitals and is shown to be simple and robust.
| S-EPMC3896198 | biostudies-other
Project description:Sulfhydryl-containing compounds, including thiols and hydrogen sulfide (H2S), play important but differential roles in biological structure and function. One major challenge in separating the biological roles of thiols and H2S is developing tools to effectively separate the reactivity of these sulfhydryl-containing compounds. To address this challenge, we report the differential responses of common electrophilic fluorescent thiol labeling reagents, including nitrobenzofurazan-based scaffolds, maleimides, alkylating agents, and electrophilic aldehydes, toward cysteine and H2S. Although H2S reacted with all of the investigated scaffolds, the photophysical response to each scaffold was significantly different. Maleimide-based, alkylating, and aldehydic thiol labeling reagents provided a diminished fluorescence response when treated with H2S. By contrast, nitrobenzofurazan-based labeling reagents were deactivated by H2S addition. Furthermore, the addition of H2S to thiol-activated nitrobenzofurazan-based reagents reduced the fluorescence signal, thus establishing the incompatibility of nitrobenzofurazan-based thiol labeling reagents in the presence of H2S. Taken together, these studies highlight the differential reactivity of thiols and H2S toward common thiol-labeling reagents and suggest that sufficient care must be taken when labeling or measuring thiols in cellular environments that produce H2S due to the potential for both false-positive and eroded responses.
| S-EPMC4063329 | biostudies-literature
Project description:We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ?1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on.
| S-EPMC5951364 | biostudies-literature
Project description:Depletion of cardiac ATP content is a characteristic feature of heart failure in patients and experimental animal models. To analyze the impact of insufficient ATP supply on heart function we inhibited cellular respiration by disulfide poisoning with the mild thiol-blocking agent, cystamine. We chose 4 month-old apolipoprotein E (apoE)-deficient mice, which are highly vulnerable to increased oxygen and ATP demands. After 4 weeks of cystamine treatment (300 mg/kg in drinking water), echocardiography and histology analyses demonstrated that apoE-deficient mice had developed heart failure with cardiac dilation. The microarray gene expression study of heart tissue from cystamine-treated apoE-deficient mice relative to untreated mice confirmed the development of heart failure showing up-regulation heart failure-specific genes by mild thiol-blocking with cystamine. Microarray gene expression profiling was performed with heart tissue isolated from three study groups: (i) cystamine-treated 5 month-old apolipoprotein- (apoE)- deficient mice with symptoms of heart failure, (ii) untreated 5 month-old apoE- deficient mice, and (iii) age-matched, untreated, non-transgenic B6 control mice.
2010-12-03 | E-GEOD-25768 | biostudies-arrayexpress
Project description:The thiol reagent dithiothreitol inhibits the activity of a core GDP-fucose-N-acetylglucosaminide alpha-6-fucosyltransferase in plasma and blood-cell homogenates, while promoting the activity of alpha-2- and alpha-3-fucosyltransferases. The latter enzymes catalyse transfer of fucose on to terminal galactose and subterminal N-acetylglucosamine residues respectively. A thiol-blocking reagent N-ethylmaleimide does not affect the activity of the alpha-6-fucosyltransferase, but inhibits the other two enzymes. These results indicate the presence of a critical disulphide linkage in the alpha-6-fucosyltransferase, and provide a means of delineation of different fucosyltransferases.
| S-EPMC1161218 | biostudies-other
Project description:2-Carboxy-D-arabinitol 1-phosphate (CA1P) phosphatase de- grades CA1P, an inhibitor associated with the regulation of ribulose bisphosphate carboxylase/oxygenase in numerous plant species. CA1P phosphatase purified from Phaseolus vulgaris was partially inactivated by oxidizing conditions during dialysis in air-equilibrated buffer. Phosphatase activity could then be stimulated 1.3-fold by dithiothreitol and also by addition of reduced thioredoxin from Escherichia coli. These effects were enhanced synergistically by the positive effector, fructose 1, 6-bisphosphate (FBP). Most notably, CA1P phosphatase activity was stimulated up to 35-fold by glutathione, and was sensitive to the ratio of reduced (GSH) to oxidized (GSSG) forms. At concentrations of glutathione approximating measured levels in chloroplasts of P. vulgaris (5 mM total S), CA1P phosphatase exhibited >20-fold stimulation by a change in the redox status of glutathione from 60 to 100% GSH. This stimulation was augmented further by reduced E. coli thioredoxin. In contrast, FBP, which activates CA1P phosphatase under reducing conditions, was strongly inhibitory in the presence of GSSG. We propose that glutathione may have an appreciable role in the light/dark regulation of CA1P phosphatase in vivo. A model for the reversible activation of CA1P phosphatase by GSH was derived based upon the various responses of the enzyme's activity to a range of thiol reagents including N-ethylmaleimide, 5, 5'-dithiobis-(2-nitrobenzoic acid) and arsenite. These data indicate that the bean enzyme contains two physically distinct sets of thiol groups that are critical to its redox regulation.
| S-EPMC1220067 | biostudies-other