China
Africa
Explore chapters and articles related to this topic
The Modification of Cystine — Cleavage of Disulfide Bonds
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
Disulfide bonds are somewhat unstable at alkaline pH (pH ≥ 13.0). This has been examined by Donovan in some detail.15 With protein-bound cystine, there is change in the spectrum with an increase in absorbance at 300 nm. This problem has been more recently studied by Florence.16 This investigation presented evidence to suggest that cleavage of disulfide bonds in proteins by base proceeds via β-elimination to form dehydroalanine and a persulfide intermediate which can decompose to form several products.
The Role of Light and Electromagnetic Fields in Maintaining Vascular Health
Published in Aruna Bakhru, Nutrition and Integrative Medicine, 2018
The heparan sulfate molecules in the matrix are constantly assembled and destroyed. They serve multiple functions for the cell lucky enough to take them up into its lysosomes. As we've seen, the sulfate provides the acidic environment that allows iron to safely break down molecular debris, generating water as a by-product rather than superoxide or the hydroxyl radical. It isn't until the very end of the digestive process in the lysosome that the sulfates are finally detached from the sugar molecules in the heparan sulfate. Now, the reducing action of the sugar can reduce the sulfate to sulfide, which likely reacts with common molecules like pyruvate to form mercaptopyruvate, and with cysteine to form cysteine persulfide (CSSH). These molecules are essentially carriers of hydrogen sulfide gas, just as molecules such as S-nitrosoglutathione (GSNO) are carriers of nitric oxide that can later be released.
Glutathione Trisulfide Prevents Lipopolysaccharide-induced Inflammatory Gene Expression in Retinal Pigment Epithelial Cells
Published in Ocular Immunology and Inflammation, 2022
Hiroshi Tawarayama, Noriyuki Suzuki, Maki Inoue-Yanagimachi, Noriko Himori, Satoru Tsuda, Kota Sato, Tomoaki Ida, Takaaki Akaike, Hiroshi Kunikata, Toru Nakazawa
The present study is the first to demonstrate that in RPE cells, GSSSG, an endogenous glutathione persulfide, can inhibit the upregulation of inflammatory mediators, including IL-1ß, IL-6, and CCL2, and that the GSSSG-mediated inhibition is partly mediated via hyperactivation of the ERK1/2 signaling pathway. These findings suggest that GSSSG is an endogenous modulator of the inflammatory responses in organisms and plays an important role in attenuating excessive inflammation, thereby preventing inflammation-induced tissue damage. The inflammatory responses of RPE cells are implicated in the development of age-related retinal-degeneration diseases.1,9,10 Thus, administration of exogenous GSSSG might be a promising treatment for such inflammation-associated diseases.
The roles of hydrogen sulfide in renal physiology and disease states
Published in Renal Failure, 2022
Jianan Feng, Xiangxue Lu, Han Li, Shixiang Wang
How does H2S perform biological functions? Recent studies have provided answers. H2S can regulate different signaling pathways that affect cell metabolism. H2S is involved in signal transmission through signaling pathways via sulfhydration, during which it reacts with cysteine residues of various target proteins to form persulfide bonds. The reactivity of sulfhydration is determined by the acid dissociation constants of cysteine residues [13]. Mustafa et al. [14] found that approximately 10–25% of liver proteins can be activated by S–sulfhydration, such as actin, tubulin, and glyceraldehyde–3–phosphate dehydrogenase. S–sulfhydration is essential for the functions of liver proteins; for example, it enhances glyceraldehyde–3–phosphate dehydrogenase activity and actin polymerization. H2S is an endothelium–derived hyperpolarizing factor that can lead to hyperpolarization and vasodilation of vascular endothelial and smooth muscle cells. This vasodilation is mainly achieved via activation of the ATP–sensitive, intermediate and small conductance potassium channels, and the most critical step for channel activation is S–sulfhydration [15]. H2S participates in inflammatory reactions as a messenger molecule, and the downstream effects of sulfhydration affect nuclear factor κB (NF–κB). NF–κB plays a key role in the inflammatory response in cells. Nil Kantha et al. [5] found that tumor necrosis factor–α (TNF–α) can stimulate the transcription of CSE to generate H2S. H2S sulfhydrates Cys38 of p65, enhancing its binding to the coactivator ribosomal protein S3, thereby regulating the nuclear functions of NF–κB. In CSE–deficient mice, p65 cannot be sulfhydrated, resulting in decreased NF–κB target gene activity. The protein tyrosine phosphatase–1B is located on the cytoplasmic face of the endoplasmic reticulum (ER) and has been implicated in ER stress signaling. H2S–induced sulfhydration of protein tyrosine phosphatase–1B participates in the ER stress response [16]. P66Shc is an upstream activator of mitochondrial redox signaling. In response to OS, p66Shc is activated through protein kinase C–bII–mediated phosphorylation at Ser36. Xie et al. [17] found that H2S downregulates the phosphorylation of p66Shc through the sulfhydration of Cys59 residue, thus reducing mitochondrial production of reactive oxygen species (ROS) and achieving antioxidant effects. Nuclear factor–erythroid 2–related factor 2 (Nrf2) is a master regulator of the antioxidant response. Normally, Nrf2 is ubiquitinated and rapidly degraded by the proteasome under the action of Kelch–like ECH–associated protein 1 (Keap1). Sodium sulfide (NaHS) has been reported to S–sulfhydrate Keap1 at Cys151 and promote Nrf2 nuclear translocation [18].