scholarly journals Catalytic Site Cysteines of Thiol Enzyme: Sulfurtransferases

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Noriyuki Nagahara
Keyword(s):  
Reduced Glutathione ◽  
Cysteine Residue ◽  
Catalytic Site ◽  
The Other ◽  
Cysteine Residues ◽  
Other Hand ◽  
Redox Active ◽  
Mercaptopyruvate Sulfurtransferase ◽  
Catalytic Processes ◽  
Thiosulfate Sulfurtransferase

Thiol enzymes have single- or double-catalytic site cysteine residues and are redox active. Oxidoreductases and isomerases contain double-catalytic site cysteine residues, which are oxidized to a disulfide via a sulfenyl intermediate and reduced to a thiol or a thiolate. The redox changes of these enzymes are involved in their catalytic processes. On the other hand, transferases, and also some phosphatases and hydrolases, have a single-catalytic site cysteine residue. The cysteines are redox active, but their sulfenyl forms, which are inactive, are not well explained biologically. In particular, oxidized forms of sulfurtransferases, such as mercaptopyruvate sulfurtransferase and thiosulfate sulfurtransferase, are not reduced by reduced glutathione but by reduced thioredoxin. This paper focuses on why the catalytic site cysteine of sulfurtransferase is redox active.

scholarly journals Interaction of glutathione analogues with Hydra attenuata γ-glutamyltransferase

1978 ◽  
Vol 175 (2) ◽  
pp. 547-553 ◽  
Author(s):  
J Danner ◽  
M H Cobb ◽  
W Heagy ◽  
H M Lenhoff ◽  
G R Marshall
Keyword(s):  
Reduced Glutathione ◽  
Cysteine Residue ◽  
The Other ◽  
Heat Denaturation ◽  
Gamma Glutamyltransferase ◽  
Gamma Glutamyl ◽  
Other Hand ◽  
Competitive Inhibitors ◽  
Hydra Attenuata ◽  
Peptide Analogues

gamma-Glutamyltransferase activity was studied in extracts of the cnidarian Hydra attenuata. The binding of gamma-glutamyl peptide analogues to the enzyme was studied by observing their effects on heat denaturation and their inhibition of p-nitroaniline release from gamma-glutamyl p-nitroanilide. Neither position-1 analogues, in which the gamma-glutamyl moiety was changed to a beta-aspartyl (beta-Asp-Abu-Gly) or an alpha-glutamyl (Glu-Abu-Gly) linkage, nor glutamate protected the enzyme against inactivation at 58 degrees C. GSH (reduced glutathione), gamma-Glu-Abu-Gly and gamma-Glu-Met on the other hand did prevent heat denaturation. GSH and analogues of GSH were competitive inhibitors of p-nitroaniline release, but those analogues in which glycine was replaced by 2-aminoisobutyrate, phenylalanine, leucine or tyrosine had Ki values that were approximately five times those of analogues with the cysteine residue replaced.

scholarly journals Catalyzed Mizoroki-Heck Reaction or C-H Activation

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 925 ◽  
Author(s):  
Sabine Berteina-Raboin
Keyword(s):  
Heck Reaction ◽  
The Other ◽  
Other Hand ◽  
Catalytic Processes ◽  
The One

In the last few decade, research conducted on the development by catalytic processes of C-C bonds formation on the one hand and on the other hand on the activation of C-H bonds has grown considerably [...]

scholarly journals The accessibility of the thiol groups on G- and F-actin of rabbit muscle

1990 ◽  
Vol 266 (2) ◽  
pp. 453-459 ◽  
Author(s):  
D F Liu ◽  
D Wang ◽  
A Stracher
Keyword(s):  
Thiol Group ◽  
Iodoacetic Acid ◽  
Drastic Change ◽  
The Other ◽  
Cysteine Residues ◽  
Rabbit Muscle ◽  
Thiol Groups ◽  
Filamentous Actin ◽  
Other Hand

The accessibility of the cysteine residues of actin from rabbit muscles to the thiol-targeted reagent 7-dimethylamino-4-methyl-(N-maleimidyl)coumarin (DACM) was investigated. Under conditions where the actin is in the unpolymerized form (G-actin), the most reactive thiol group was Cys-257, suggesting that it was located on the surface of the actin molecule. The selective modification of Cys-374 for this reagent as reported by Sutoh [(1982) Biochemistry 21, 3654-3661] was not observed. Cys-10, Cys-217 and Cys-374 were much less reactive and only gradually became extensively modified when the concentration of DACM approached 5 molar equivalents of actin. Presumably these thiol groups were located further inward away from the surface or situated in a different environment that rendered them less reactive. On the other hand, Cys-285 was completely inaccessible and presumably was buried. The lack of preferential labelling of Cys-374 by DACM is incompatible with the finding with iodoacetic acid as the reagent as reported by Elzinga & Collins [(1975) J. Biol. Chem. 250, 5897-5905]. This discrepancy, however, might well be due to the different reagents employed. The DACM-G-actin largely retained its competence for polymerization. Upon polymerization of G-actin, practically all the thiol groups became inaccessible to DACM, suggesting that a drastic change occurred in the conformation of actin units in the transition of monomers to filamentous actin.

Mechanism of detoxication of some organophosphorus compounds: the role of glutathione-dependent demethylation

1968 ◽  
Vol 46 (8) ◽  
pp. 885-892 ◽  
Author(s):  
A. Morello ◽  
A. Vardanis ◽  
E. Y. Spencer
Keyword(s):  
Mouse Liver ◽  
Organophosphorus Compounds ◽  
Reduced Glutathione ◽  
The Other ◽  
Supernatant Fraction ◽  
Geometrical Isomers ◽  
General Role ◽  
Dimethyl Phosphate ◽  
Other Hand

The detoxication of the geometrical isomers of Bomyl® (dimethyl-1,3-dicarbomethoxy-1-propen-2-yl phosphate) and Phosdrin® (mevinphos, dimethyl-1-carbomethoxy-1-propen-2-yl phosphate) by mouse liver has been studied. Most of the degrading activity for Phosdrin isomers was found in the supernatant fraction, whereas for Bomyl isomers it was equally distributed between the microsomal and the supernatant fractions. cis-Phosdrin is degraded in a system which requires reduced glutathione, the metabolites being cis-monomethyl-1-carbomethoxy-1-propen-2-yl phosphate (cis-desmethyl-Phosdrin)and S-methylglutathione. On the other hand, tras-Phosdrin and both Bomyl isomers were degraded to dimethyl phosphate. A method for the synthesis of cis-thiono-Bomyl is also reported. The possible general role of glutathione in the degradation of organophosphorus compounds is discussed.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

Don’t Put Me in This Group

2019 ◽  
Vol 50 (2) ◽  
pp. 80-93
Author(s):  
Jort de Vreeze ◽  
Christina Matschke
Keyword(s):  
Positive Emotions ◽  
Negative Emotions ◽  
Negative Information ◽  
The Self ◽  
The Other ◽  
Other Hand ◽  
Group Memberships

Abstract. Not all group memberships are self-chosen. The current research examines whether assignments to non-preferred groups influence our relationship with the group and our preference for information about the ingroup. It was expected and found that, when people are assigned to non-preferred groups, they perceive the group as different to the self, experience negative emotions about the assignment and in turn disidentify with the group. On the other hand, when people are assigned to preferred groups, they perceive the group as similar to the self, experience positive emotions about the assignment and in turn identify with the group. Finally, disidentification increases a preference for negative information about the ingroup.

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