scholarly journals The effect of chemical modifications induced in insulin on the reactivity of the interchain disulphide bonds towards sodium sulphite

1968 ◽  
Vol 108 (2) ◽  
pp. 247-255 ◽  
Author(s):  
A. Massaglia ◽  
F. Pennisi ◽  
U. Rosa ◽  
S. Ronca-Testoni ◽  
C. A. Rossi
Keyword(s):  
Biological Activity ◽  
Mode Of Action ◽  
High Reactivity ◽  
Sodium Sulphite ◽  
Thiol Groups ◽  
Chemical Modifications ◽  
Amperometric Titration ◽  
Disulphide Bonds ◽  
Native Insulin

The reactivity of the three disulphide bridges of insulin towards sodium sulphite was studied by amperometric titration of the liberated thiol groups. In the native, acetylated or succinylated molecule two bridges react at pH7, but in the methylated or phenylcarbamoylated molecule only one bridge reacts. All three bridges react in all derivatives in 8m-urea or at pH9. Loss in biological activity parallels the loss in reactivity of one of the bridges during methylation. It is suggested that change in reactivity of the S·S bonds reflects the occurrence of a conformational modification of the protein. The possibility is discussed that the unusually high reactivity of the S·S bonds in native insulin depends strictly on the integrity of the native molecule, suggesting that S·S bonds are in some way involved in the hormone's mode of action.

scholarly journals Thiol-Modification as Important Mode of Action for Allicin from Garlic (Allium sativum)

Proceedings ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 27 ◽  
Author(s):  
Martin C. H. Gruhlke
Keyword(s):  
Molecular Weight ◽  
Biological Activity ◽  
Active Compound ◽  
Mode Of Action ◽  
Allium Sativum ◽  
Cysteine Residues ◽  
Low Molecular Weight ◽  
Thiol Groups ◽  
Ancient Times ◽  
In Cells

Garlic is a common ingredient in food, normally used as spice but is also used since ancient times for its health beneficial activity. The thiosulfinate allicin is the first active compound in freshly damaged garlic tissue and reacts with thiol-groups. Hence, allicin is able to modify thiol groups, both of protein cysteine-residues and low-molecular weight thiols like glutathione. This thiol-modification is supposed to be an important mechanism for allicin’s biological activity. Here, the mechanisms and possible targets for allicin in cells are discussed.

scholarly journals A convenient method of preparation of high-activity urease from Canavalia ensiformis by covalent chromatography and an investigation of its thiol groups with 2,2'-dipyridyl disulphide as a thiol titrant and reactivity probe

1976 ◽  
Vol 159 (2) ◽  
pp. 245-257 ◽  
Author(s):  
R Norris ◽  
K Brocklehurst
Keyword(s):  
Convenient Method ◽  
Specific Activity ◽  
Class Ii ◽  
High Reactivity ◽  
Class I ◽  
Thiol Groups ◽  
Class Iii ◽  
Active Centre ◽  
Class Ib ◽  
Covalent Chromatography

1. A convenient method of preparation of jack-bean urease (EC3.5.1.5) involving covalent chromatography by thiol-disulphide interchange is described. 2. Urease thus prepared has specific activity comparable with the highest value yet reported (44.5 ± 1.47 kat/kg, Km = 3.32 ± 0.05 mM; kcat. = 2.15 × 104 ± 0.05 × 104s-1 at pH7.0 and 38°C). 3. Titration of the urease thiol groups with 2,2'-dipyridyl disulphide (2-Py-S-S-2-Py) and application of the method of Tsou Chen-Lu [(1962) Sci. Sin.11, 1535-1558] suggests that the urease molecule (assumed to have mol.wt. 483000 and ε280 = 2.84 × 105 litre·mol-1-cm-1) contains 24 inessential thiol groups of relatively high reactivity (class-I), six ‘essential’ thiol groups of low reactivity (class-II) and 54 buried thiol groups (class-III) which are exposed in 6M-guanidinium chloride. 4. The reaction of the class-I thiol groups with 2-Py-S-S-2-Py was studied in the pH range 6-11 at 25°C(I = 0.1 mol/l) by stopped-flow spectrophotometry, and the analogous reaction of the class-II thiol groups by conventional spectrophotometry. 5. The class-I thiol groups consist of at least two sub-classes whose reactions with 2-Py-S-S-2-Py are characterized by (a) pKa = 9.1, k = 1.56 × 104M-1·s-1 and (b) pKa = 8.1, k = 8.05 × 102M-1·s-1 respectively. The reaction of the class-II thiol groups is characterized by pKa = 9.15 and k = 1.60 × 102M-1·s-1. 6. At pH values 7-8 the class-I thiol groups consist of approx. 50% class-Ia groups and 50% class-Ib groups. The ratio class Ia/class Ib decreases as the pH is raised according to a pKa value ≥ approx. 9.5, and at high pH the class-I thiol groups consist of at most 25% class-Ia groups and at least 75% class-Ib groups. 7. The reactivity of the class-II thiol groups towards 2-Py-S-S-2-Py is insensitive to the nature of the group used to block the class-I thiols. 8. All the ‘essential’ thiol groups in urease appear to be eeactive only as uncomplicated thiolate ions. The implications of this for the active-centre chemistry of urease relative to that of the thiol proteinases are discussed.

scholarly journals Isomerization of all-trans-retinoic acid to 9-cis-retinoic acid

1994 ◽  
Vol 299 (2) ◽  
pp. 459-465 ◽  
Author(s):  
J Urbach ◽  
R R Rando
Keyword(s):  
Biological Activity ◽  
Retinoic Acid ◽  
Liver Microsomes ◽  
Equilibrium Concentration ◽  
Bovine Liver ◽  
Thiol Groups ◽  
First Order ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid ◽  
Liver Membranes

The discovery of the biological activity of 9-cis-retinoic acid raises questions as to its mode of biosynthesis. A simple mechanism involves the direct isomerization of all-trans-retinoic acid to 9-cis-retinoic acid. It is shown here that bovine liver membranes, but not supernatant fractions, can isomerize all-trans-retinoic acid into 9-cis-retinoic acid and 13-cis-retinoic acid. The concentration of 9-cis-retinoic acid generated approaches its equilibrium concentration, which is determined here to be approximately 15%. However, the isomerization process could not be shown to be saturable, and is first-order in all-trans-retinoic acid in the concentration range measured (8.3 nM to 3 microM). Isomerization reactions measured using bovine liver microsomes appear to be mediated by thiol groups, as they can be blocked by group-specific thiol-blocking reagents such as N-ethylmaleimide. It is interesting to note that the non-stereospecific behaviour observed here mimics what is observed when all-trans-retinoic acid is applied to cells. Finally, significant formation of 9-cis-retinoids was not found when the reaction was carried out with liver microsomes and either all-trans-retinol or all-trans-retinal.

scholarly journals AFN-1252 is a potent inhibitor of enoyl-ACP reductase from B urkholderia pseudomallei -Crystal structure, mode of action, and biological activity

2015 ◽  
Vol 24 (5) ◽  
pp. 832-840 ◽  
Author(s):  
Krishnamurthy Narasimha Rao ◽  
Anirudha Lakshminarasimhan ◽  
Sarah Joseph ◽  
Swathi U. Lekshmi ◽  
Ming-Seong Lau ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Biological Activity ◽  
Mode Of Action ◽  
Potent Inhibitor ◽  
Enoyl Acp Reductase

scholarly journals Chemical modifications of natural triterpenes—glycyrrhetinic and boswellic acids: evaluation of their biological activity

Tetrahedron ◽  
2008 ◽  
Vol 64 (51) ◽  
pp. 11541-11548 ◽  
Author(s):  
G.S.R. Subba Rao ◽  
Paturu Kondaiah ◽  
Sanjay K. Singh ◽  
Palaniyandi Ravanan ◽  
Michael B. Sporn
Keyword(s):  
Biological Activity ◽  
Chemical Modifications ◽  
Boswellic Acids

Determination of —SH and —SS— groups in proteins. I. A reassessment of the use of methylmercuric iodide

1968 ◽  
Vol 46 (19) ◽  
pp. 3033-3040 ◽  
Author(s):  
W. F. Forbes ◽  
C. R. Hamlin
Keyword(s):  
Quantitative Determination ◽  
Disulfide Bond ◽  
Bond Cleavage ◽  
Reaction Times ◽  
High Reactivity ◽  
Insoluble Protein ◽  
Amperometric Titration ◽  
General Belief ◽  
Experimental Procedure

Amperometric titration with methylmercuric iodide was found to be unsatisfactory for the quantitative determination of —SH and —SS— values in several soluble proteins. It is concluded that the "high reactivity" of the mercurial has previously been overemphasized. Consistent values can, however, be obtained by permitting protein samples to react with an excess of the mercurial, for about 100 h, followed by the polarographic estimation of the remaining reagent. Contrary to general belief, this procedure was found to be more precise than amperometric titration, and, if appropriate precautions are taken, it is applicable to considerably smaller amounts (<0.5 μmole —SH or —SS—) of either soluble or insoluble protein. The necessary experimental procedure is described and results are reported for several proteins. For the compounds studied, methylmercuric iodide did not react at non-sulfhydryl sites, and did not additionally bind to the mercaptides formed; there was no indication of disulfide bond cleavage, despite the long reaction times used.

Studies on the Mode of Action of Insulin: Properties and Biological Activity of an Insulin-Dextran Complex

Endocrinology ◽  
1972 ◽  
Vol 90 (5) ◽  
pp. 1220-1230 ◽  
Author(s):  
FUJIO SUZUKI ◽  
YASUSHI DAIKUHARA ◽  
MASAYOSHI ONO ◽  
YOSHIRO TAKEDA
Keyword(s):  
Biological Activity ◽  
Mode Of Action

scholarly journals Rapid and selective modification of phosphoserine residues catalysed by Ba2+ ions for their detection during peptide microsequencing

1991 ◽  
Vol 280 (1) ◽  
pp. 261-265 ◽  
Author(s):  
M F Byford
Keyword(s):  
Amino Acid ◽  
Sequence Analysis ◽  
Metal Ions ◽  
Ion Concentration ◽  
Thiol Groups ◽  
Disulphide Bonds ◽  
Rate Of Reaction ◽  
Alkaline Conditions ◽  
Beta Elimination ◽  
Alpha Beta

The beta-elimination of phosphoserine residues by dilute alkali is catalysed by the presence of group II metal ions. The use of 0.1 M-Ba (OH)2 catalysed the rate of beta-elimination of phosphoserine by more than two orders of magnitude compared with the use of NaOH at the same OH-ion concentration. Serine and threonine residues are unaffected by this treatment. Free thiol groups and disulphide bonds are labile to these conditions, but carboxymethylcysteine is stable. The rate of beta-elimination of O-glycosidically linked moieties is not catalysed under these conditions, and the rate of reaction is thus two orders of magnitude slower than for phosphoserine. This specific catalysis was readily exploited in the rapid and selective modification of phosphoserine residues under mildly alkaline conditions with the nucleophile methylamine via the alpha beta-desaturated dehydroalanine intermediate to yield the beta-methylaminoalanine residue. This modified residue could be easily detected on sequence analysis and in amino acid compositions.

scholarly journals Formation of one or more intrachain disulphide bonds is required for the intracellular processing and transport of CD36

1997 ◽  
Vol 328 (2) ◽  
pp. 635-642 ◽  
Author(s):  
Paola GRUARIN ◽  
Roberto SITIA ◽  
Massimo ALESSIO
Keyword(s):  
Scavenger Receptor ◽  
Extracellular Domain ◽  
Low Density Lipoproteins ◽  
Cysteine Residues ◽  
Thiol Groups ◽  
Wild Type ◽  
Mobility Shift ◽  
Disulphide Bonds ◽  
Gel Mobility Shift ◽  
Triton X

In monocytes/macrophages, CD36 is thought to have a role as a scavenger receptor, mediating the phagocytosis of apoptotic cells and the endocytic uptake of oxidized low-density lipoproteins and fatty acids. The proposed topology of CD36 predicts that, of ten cysteine residues, six lie in the extracellular domain, whereas four are equally distributed in the two short terminal tails flanking the N-terminal and C-terminal hydrophobic stretches. Here we investigate the formation of intrachain disulphide bonds, on the basis of the assumption that the cysteine residues present in the luminal domains are generally oxidized, whereas those in the cytosol are reduced. As revealed by gel mobility-shift assays, disulphide bonds are present in the extracellular domain of the CD36 molecule. The formation of these bonds is required for the transport of CD36 from endoplasmic reticulum to Golgi. Furthermore reactive thiol groups are present in the CD36 sequence, which upon lysis form an intrachain extra loop as an artifact. This disulphide bond is not formed in either (1) truncated CD36 lacking the two C-terminal cysteine residues or (2) Triton X-100-insoluble wild-type CD36 molecules, suggesting that, in this fraction, the C-terminal thiol groups are modified.

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