The influence of haptoglobin on the reactivity of the –SH groups of hemoglobin

1969 ◽  
Vol 47 (12) ◽  
pp. 1205-1208 ◽  
Author(s):  
B. Malchy ◽  
G. H. Dixon
Keyword(s):  
Conformation Change ◽  
Sulfhydryl Reagents ◽  
Sh Groups ◽  
Rate Of Reaction

The rate of reaction of the β93 sulfhydryl of hemoglobin with iodoacetamide and 2,2′-, and 4,4′- dithiodipyridine is much slower when the hemoglobin is bound by haptoglobin than when it is free. However, these sulfhydryl reagents will react with the haemoglobin–haptoglobin complex, and the reaction of the complex with iodoacetamide is still at position β93. The results suggest that haptoglobin might induce a conformation change on oxyhemoglobin which is similar to that occurring upon deoxygenation.

Mg2+-activated ATP hydrolysis and sulfhydryl groups in membranes from human erythrocytes

1970 ◽  
Vol 48 (5) ◽  
pp. 604-612 ◽  
Author(s):  
Frances M. Smith ◽  
Jacob A. Verpoorte
Keyword(s):  
Atp Hydrolysis ◽  
Enzymatic Reaction ◽  
Maximal Activity ◽  
Maximum Activity ◽  
Human Erythrocytes ◽  
Sulfhydryl Groups ◽  
Sulfhydryl Reagents ◽  
Rate Of Reaction ◽  
Rate Profile ◽  
Sigmoid Shape

The ATP-hydrolyzing activity of membranes prepared from human erythrocytes depends on the presence of Mg2+ ions. Maximum activity is observed when the concentrations of Mg2+ and ATP are equal. The pH–rate profile of the enzymatic reaction shows a maximum at pH 7.8. The ATP-hydrolyzing activity has decreased to half the maximal activity at pH 6.3 and 9.8, respectively. The enzyme is inhibited by sulfhydryl reagents like p-chloromercuribenzoate (p-CMB) and N-ethylmaleimide. Membranes that are titrated with NaOH or treated with p-CMB lose up to 30% of their protein content. This loss is reversed when Mg2+ or Mg2+ plus ATP is added. However, neither Mg2+ nor Mg2+ plus ATP detectably alters the rate of reaction between the sulfhydryl groups and specific reagents, nor protects the ATP-hydrolyzing activity from inhibition by p-CMB. The amount of protein which dissociates from the membrane increases with pH. The curve describing this extraction has a sigmoid shape with an inflection point at pH 10.2. Maximum solubilization is obtained at pH 11.2. Thus the results indicate that sulfhydryl groups and also the structure of the membrane are important for the ATP-hydrolyzing activity.

Investigations into the role of sulfhydryl groups in the mechanism of action of the nitrates

1982 ◽  
Vol 60 (10) ◽  
pp. 1261-1266 ◽  
Author(s):  
J. A. Moffat ◽  
P. W. Armstrong ◽  
G. S. Marks
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Mechanism Of Action ◽  
Active Site ◽  
Sulfhydryl Reagents ◽  
Response Curves ◽  
Sh Groups ◽  
Nitrobenzoic Acid ◽  
Sh Group

The mechanism by which nitroglycerin (GTN) initiates relaxation in vascular smooth muscle is not known. According to one hypothesis a specific nitrate receptor exists with a key sulfhydryl (SH) group in the active site. The current study was performed with sulfhydryl reagents in helical strips of the canine medial saphenous vein from 20 dogs to examine the role of the SH group in the action of GTN. The reagents used were 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) and p-chloromercuribenzoate (PCMB) which bind to and inactivate SH groups, and dithiothreitol (DTT), an SH reducing agent. It was anticipated that DTNB and PCMB would decrease the sensitivity to GTN while DTT might increase the sensitivity to GTN. Treatment of strips with PCMB and DTNB did not alter the dose–response curves for GTN. In contrast, following DTT treatment (1 × 10−4 M) the maximum response to GTN (10−5 M) was significantly reduced from 80.3% ± 4.0 (SD) in control strips to 46.9% ± 4.4 (SD) in the treated strips. These data suggest that relaxation induced by GTN in vascular smooth muscle occurs by a mechanism other than interaction with membrane SH groups.

scholarly journals THE ROLE OF SULFHYDRYL GROUPS IN THE BLEACHING AND SYNTHESIS OF RHODOPSIN

1952 ◽  
Vol 35 (5) ◽  
pp. 797-821 ◽  
Author(s):  
George Wald ◽  
Paul K. Brown
Keyword(s):  
Protein Denaturation ◽  
Sulfhydryl Groups ◽  
Amino Groups ◽  
Hydrogen Atoms ◽  
Sulfhydryl Reagents ◽  
Excitation Process ◽  
Sh Groups ◽  
Sulfhydryl Compound

The condensation of retinene1 with opsin to form rhodopsin is optimal at pH about 6, a pH which favors the condensation of retinene1 with sulfhydryl rather than with amino groups. The synthesis of rhodopsin, though unaffected by the less powerful sulfhydryl reagents, monoiodoacetic acid and its amide, is inhibited completely by p-chloromercuribenzoate (PCMB). This inhibition is reversed in part by the addition of glutathione. PCMB does not attack rhodopsin itself, nor does it react with retinene1. Its action in this system is confined to the —SH groups of opsin. Under some conditions the synthesis of rhodopsin is aided by the presence of such a sulfhydryl compound as glutathione, which helps to keep the —SH groups of opsin free and reduced. By means of the amperometric silver titration of Kolthoff and Harris, it is shown that sulfhydryl groups are liberated in the bleaching of rhodopsin, two such groups for each retinene1 molecule that appears. This is true equally of rhodopsin from the retinas of cattle, frogs) and squid. The exposure of new sulfhydryl groups adds an important element to the growing evidence that relates the bleaching of rhodopsin to protein denaturation. The place of sulfhydryl groups in the structure of rhodopsin is still uncertain. They may be concerned directly in binding the chromophore to opsin; or alternatively they may furnish hydrogen atoms for some reductive change by which the chromophore is formed from retinene1. In the amperometric silver titration, the bleaching of rhodopsin yields directly an electrical variation. This phenomenon may have some fundamental connection with the role of rhodopsin in visual excitation, and may provide a model of the excitation process in general.

scholarly journals STUDIES ON THE MECHANISM OF HYDROGEN TRANSPORT IN ANIMAL TISSUES

1943 ◽  
Vol 26 (4) ◽  
pp. 391-404 ◽  
Author(s):  
V. R. Potter ◽  
K. P. DuBois
Keyword(s):  
Succinic Dehydrogenase ◽  
Sulfhydryl Group ◽  
Carboxyl Groups ◽  
Common Denominator ◽  
Hydrogen Transport ◽  
Animal Tissues ◽  
Sulfhydryl Reagents ◽  
Sh Groups ◽  
Copper Zinc ◽  
Sulfhydryl Compounds

1. The mechanism of succinic dehydrogenase action was studied by means of inhibitors. 2. The enzyme is inhibited by a large number of diverse compounds whose only common denominator appears to be their ability to react with SH groups. These compounds include quinonoid structures, sulfhydryl reagents, sulfhydryl compounds, copper, zinc, selenite, and arsenite. 3. In contrast to the above inhibitors, the action of malonate does not appear to involve sulfhydryl groups and is explained on the basis of its affinity for the enzyme groups which react with the carboxyl groups of succinate. 4. The action of malonate and the sulfhydryl reactants is mutually exclusive, and this fact suggests the conclusion that the sulfhydryl group of the enzyme is located between the carboxyl affinity points. 5. On the basis of the deduced structure of the succinate-activating center of the enzyme, it is suggested that the enzyme may function by oscillating between the EnSH and EnS· forms, rather than by a thiol-disulfide equilibrium.

Inactivation of Streptococcal Bacteriophage by Sulfhydryl Reagents.

1963 ◽  
Vol 114 (3) ◽  
pp. 822-826 ◽  
Author(s):  
D. Kessler ◽  
R. M. Krause
Keyword(s):  
Sulfhydryl Reagents

Notizen: Effect of Magnetic Field on Ascorbic Acid Oxidase Activity, I

1986 ◽  
Vol 41 (3) ◽  
pp. 355-358 ◽  
Author(s):  
V. S. Ghole ◽  
P. S. Damle ◽  
W. H.-P. Thiemann
Keyword(s):  
Magnetic Field ◽  
Ascorbic Acid ◽  
Homogeneous Magnetic Field ◽  
Acid Oxidase ◽  
High Substrate Concentration ◽  
Ascorbic Acid Oxidase ◽  
Rate Of Reaction ◽  
Substrate Concentrations ◽  
Burk Plot

A homogeneous magnetic field of 1.1 T strength exhibits a significant influence on the activity of the enzyme ascorbic acid oxidase in vitro. A Lineweaver-Burk plot of the reaction shows the typical pattern of a mixed-type inhibition, i.e. a larger rate of reaction at low substrate concentrations and a smaller rate of reaction at high substrate concentration than that of the control without magnetic field applied.

scholarly journals Effects of heavy metal on rat liver microsomal Ca2(+)-ATPase and Ca2+ sequestering. Relation to SH groups.

1990 ◽  
Vol 265 (4) ◽  
pp. 2184-2189
Author(s):  
G H Zhang ◽  
M Yamaguchi ◽  
S Kimura ◽  
S Higham ◽  
N Kraus-Friedmann
Keyword(s):  
Heavy Metal ◽  
Rat Liver ◽  
Sh Groups

Green synthesized Ag-TiO2 for degradation of organic dye through visible light driven photo-reactor and its kinetics

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Titikshya Mohapatra ◽  
Sakshi Manekar ◽  
Vijyendra Kumar Sahu ◽  
Ashwini Kumar Soni ◽  
Sudip Banerjee ◽  
...  
Keyword(s):  
Visible Light ◽  
Mangifera Indica ◽  
Band Gap Energy ◽  
Photo Degradation ◽  
X Ray ◽  
Green Approach ◽  
Vis Spectroscopy ◽  
Rate Of Reaction ◽  
Visible Light Driven ◽  
Modification Of Titanium

Abstract This study reports a green approach for the modification of titanium dioxide (TiO2) nanoparticles with immobilization of silver nanoparticles. One of the natural sources i.e., Mangifera indica leaf extract was utilized as reducing and capping agent for the fabrication of Ag-TiO2 nanocatalyst. Further, the surface morphology and band-gap energy of prepared Ag-TiO2 were analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and UV–Vis spectroscopy. Also, it was characterized by X-ray Powder Diffraction (XRD) which provides the information regarding the crystallinity of the Ag-TiO2. Subsequently, photo activity of Ag-TiO2 was investigated for the degradation of methylene blue (MB) dye wastewater through visible light driven photoreactor. The Ag-TiO2 provided highest (68%) of photo-degradation efficiency within 110 min for 7.81 × 10−5 mol/L initial MB concentration at pH 8 by using 0.19 g/L photocatalyst. Further, addition of 10 mM H2O2 boost up the MB photodegradation to 74%. The kinetic study confirmed the MB degradation followed first order rate of reaction.

scholarly journals Extra-platelet low-molecular-mass thiols mediate the inhibitory action of S-nitrosoalbumin on human platelet aggregation via S-transnitrosylation of the platelet surface

Amino Acids ◽  
2021 ◽  
Author(s):  
Dimitrios Tsikas
Keyword(s):  
Platelet Aggregation ◽  
Molecular Mass ◽  
Underlying Mechanism ◽  
Selective Extraction ◽  
Post Translational Modification ◽  
No Donor ◽  
Platelet Surface ◽  
Sh Groups ◽  
Human Platelet Aggregation ◽  
Inhibitory Potential

AbstractNitrosylation of sulfhydryl (SH) groups of cysteine (Cys) moieties is an important post-translational modification (PTM), often on a par with phosphorylation. S-Nitrosoalbumin (ALB-Cys34SNO; SNALB) in plasma and S-nitrosohemoglobin (Hb-Cysβ93SNO; HbSNO) in red blood cells are considered the most abundant high-molecular-mass pools of nitric oxide (NO) bioactivity in the human circulation. SNALB per se is not an NO donor. Yet, it acts as a vasodilator and an inhibitor of platelet aggregation. SNALB can be formed by nitrosation of the sole reduced Cys group of albumin (Cys34) by nitrosating species such as nitrous acid (HONO) and nitrous anhydride (N2O3), two unstable intermediates of NO autoxidation. SNALB can also be formed by the transfer (S-transnitrosylation) of the nitrosyl group (NO+) of a low-molecular-mass (LMM) S-nitrosothiol (RSNO) to ALB-Cys34SH. In the present study, the effects of LMM thiols on the inhibitory potential of ALB-Cys34SNO on human washed platelets were investigated. ALB-Cys34SNO was prepared by reacting n-butylnitrite with albumin after selective extraction from plasma of a healthy donor on HiTrapBlue Sepharose cartridges. ALB-Cys34SNO was used in platelet aggregation measurements after extended purification on HiTrapBlue Sepharose and enrichment by ultrafiltration (cutoff, 20 kDa). All tested LMM cysteinyl thiols (R-CysSH) including l-cysteine and L-homocysteine (at 10 µM) were found to mediate the collagen-induced (1 µg/mL) aggregation of human washed platelets by SNALB (range, 0–10 µM) by cGMP-dependent and cGMP-independent mechanisms. The LMM thiols themselves did not affect platelet aggregation. It is assumed that the underlying mechanism involves S-transnitrosylation of SH groups of the platelet surface by LMM RSNO formed through the reaction of SNALB with the thiols: ALB-Cys34SNO + R-CysSH ↔ ALB-Cys34SH + R-CysSNO. Such S-transnitrosylation reactions may be accompanied by release of NO finally resulting in cGMP-dependent and cGMP-independent mechanisms.

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