Glutathione
Ruth G. Alscher, John L. Hess in Antioxidants in Higher Plants, 2017
A major function of GSH in the protection of cells against the toxic effects of free radicals is to keep the free radical scavenger ascorbic acid in its reduced, and hence, active form. Dehydroascorbate reductase (DHAR) uses reduced glutathione as an electron donor for the reduction of dehydroascorbate to ascorbate. Its role in ascorbic acid metabolism has been reviewed by Loewus.13 The enzyme has been purified from spinach leaves.14,15 It is highly specific for GSH and inhibited by high concentrations of dehydroascorbate. Thiol groups are involved in catalysis, as SH-reagents deactivate the enzyme.14 Most of the DHAR activity in peas is localized in the chloroplast,8 but the enzyme from Euglena gracilis has been shown to be entirely cytosolic.16
Proteins in Cosmetics
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
Soluble native collagen could be considered a significant exception. It is well proved that the triple-helical structure of tropocollagen and its ability to reticulate by forming side interchain linkages are fundamental for the building of the fibrous hydrophilic skeleton in the connective tissues, and that this is the consequence of its characteristic amino acid pattern, with repeating sequences of glycine-proline-hydroxyproline and a glycine residue every three amino acids. These features are the basis of the biological properties of collagen in living tissues and possibly play important roles (together with molecular size and net charge) for the film-forming and moisturizing effects that exogenous native collagen exhibits on the skin surface. When collagen is denaturated or hydrolyzed, the spatial architecture of the original protein is likely to be entirely lost and relationships between cosmetic effects and three-dimensional structure can no longer be invoked. Thiol Groups and Disulfide Bridges
Morphology and Properties of Hair
Dale H. Johnson in Hair and Hair Care, 2018
As indicated, this reaction is reversible. However, if for example the disulphide bond —SbSc— were under mechanical stress, whereas the reformed bond —SaSc were at lower or no stress, the reaction would be favored in the forward direction. The reaction results in relaxation of stress in an extended keratin structure, the interchange favoring the breakdown of bonds under stress and the reformation of new bonds in equilibrium with the extended system. The number of ionized sulfhydryl groups may be quite limited, in the native α-keratin structure, less than about 1 thiol of the residue of cysteine existing for every 10 disulfides of cystine. However, one thiol group may progressively be involved via a “zipper” reaction in the interchanging in turn of many stressed disulfide bonds, the thiol group being continuously replaced at each interchange. Further, in the particular case of the setting of hair in a predetermined configuration, the interchange reaction may be speeded up by the chemical production of more thiol groups through the reduction of disulfide bonds present in the keratin structure. This reduction may be obtained by a number of reagents, in particular thiols such as thioglycollic acid or mercapto ethanol. It should be noted that the thiol group must be ionized for the sulfydril-disulfide interchange to occur. The interchange is therefore also favored by neutral and alkaline conditions, and is prevented from occurring under acid conditions.
Thiol/disulphide homeostasis in manic episode and remission phases of bipolar disorder
Published in Nordic Journal of Psychiatry, 2018
Merve Cingi Yirün, Kübranur Ünal, Onur Yirün, Osman Hasan Tahsin Kiliç, Özcan Erel
‘Thiol’ refers to an organic compound that is containing a sulfhydryl group (SH) [10]. The main thiol sources in plasma are albumin thiols and protein thiols. In addition, low-molecular-weight thiols such as cysteine (Cys), cysteinylglycine, glutathione, homocysteine and γ-glutamylcysteine contributes to plasma thiol contents [11]. Thiols can undergo oxidation reaction via oxidant molecules and originate disulphide bonds [12]. Under appropriate circumstances, these disulphide bonds can again be reduced into thiol groups; so that the dynamic thiol–disulphide homeostasis is preserved [13]. This homeostasis is important for maintaining the oxidative balance, as well as for many other functions in the organism like signal transduction and programmed cell death [14,15]. Recent researches has focused on the possible impairment of dynamic thiol–disulphide homeostasis in chronical diseases such as diabetes mellitus, atherosclerosis, chronical renal disease, rheumatoid arthritis multiple sclerosis and amyotrophic lateral sclerosis [16–20]. Scientific data points that cysteine, glutathione and thiol metabolism alterations are commonly seen in chronic and inflammatory diseases. Since BD is an important chronical psychiatric condition in which oxidative balance was previously found to be impaired; this study aims to investigate thiol–disulphide homeostasis in bipolar patients, by comparing patients in remission (RE) and patients with manic episode (MA) and also by evaluating them together with healthy controls. As far as we know, this is one of the first studies focusing on plasma dynamic thiol–disulphide status in BD.
Evaluation of the role of thiol / disulfide homeostasis in the etiology of idiopathic male infertility with a novel and automated assay
Published in Systems Biology in Reproductive Medicine, 2022
Uygar Micoogullari, Mehmet Caglar Cakici, Furkan Umut Kilic, Erdem Kisa, Burak Ozcift, Alper Caglayan, Salim Neselioglu, Omer Faruk Karatas, Ozcan Erel
Thiol-disulfide homeostasis is vital because it is involved in numerous functions such as detoxification, apoptosis, antioxidant protection, signal transduction, as well as regulation of transcription factors, enzymatic activity, and signaling mechanisms (Circu and Aw 2010; Erel and Neselioglu 2014; Cabrillana et al. 2016; Alsalman et al. 2018). Thiols have strong antioxidant capacities in their sulfhydryl groups, containing sulfur and hydrogen atoms covalently bonded to a carbon atom. This disulfide bond is also called a disulfide bridge or SS-bond. Total thiol represents the total number of reducible/oxidizable sulfur atoms in serum. It denotes both the two sulfides in each disulfide and the sum of one sulfur atom in each native thiol. Thiols play a crucial role in protecting cells from the harmful effects of ROS (Erel and Neselioglu 2014; Eren et al. 2015). The majority of the plasma thiol pool consists primarily of albumin and other proteins. A small portion consists of low molecular weight thiols such as glutathione, cysteine, cysteinyl glycine, γ-glutamylcysteine, and homocysteine (Erel and Neselioglu 2014). ROS oxidize thiol groups of proteins, cysteine residues, and low molecular weight compounds to form reversible disulfide bond structures. The thiol-disulfide balance can be reached by reducing those disulfide bonds to thiols again. Thiols in the blood are oxidized first in response to an increase in ROS (Erel and Neselioglu 2014).
Redox status on different regions of the central nervous system of obese and lean rats treated with green tea extract
Published in Nutritional Neuroscience, 2019
Rita Cassia Macedo, Eduardo Fernandes Bondan, Rosemari Otton
However, GT treatment restored the GFAP expression induced by cafeteria diet, probably by reducing inflammation in this brain region. Silva et al.36 also demonstrated that GT reduced the expression of GFAP and oxidative stress in diabetic rats. Regarding the cerebral cortex, it was evident that supplementation with GT extract have beneficial effects this brain region to oxidative-protein damage, as shown by the reduced number of carbonyl groups and increased number of free thiol groups promoted by GT (Fig. 2). The redox state of thiol groups in cells is involved in signaling processes and pathways mediating reactive oxygen species production.37 Recent research has shown that many dietary phytochemicals that promote the health of the CNS might act as moderate pro-oxidant agents.38 Some phytochemicals can induce positive antioxidant responses by imposing mild stress on neural cells, enhancing GSH and other thiol groups, which increases the scavenging capacity of CNS. Therefore, the previously acquired thiol increment enhances the ability of neural tissues to cope with more severe oxidative stress induced by infectious agents or pathological processes, increasing resistance against neurodegenerative diseases. This mechanism is known as the ‘neurohormesis’ principle and is usually associated with enhanced neurogenesis, synaptic plasticity and resistance to oxidative injury imposed by neurodegenerative disease.38
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