Disulfide cystine

Cysteine [52-90 ] is a thiol-bearing amino acid which is readily isolated from the hydrolysis of protein. There ate only small amounts of cysteine and its disulfide, cystine, in living tissue (7). Glutathione [70-18-8] contains a mercaptomethyl group, HSCH2, and is a commonly found tripeptide in plants and animals. Coenzyme A [85-61-0] is another naturally occurring thiol that plays a central role in the synthesis and degradation of fatty acids. 

Aminophenyl disulfide Cystine, 2-Nitrophenyl disulfide Methyl disulfide, p-tolyl disulfide Benzyl disulfide Naphthothiophenes (NTH)... 

Figure 9-12. Co-ordinated thiols or thiolates are readily oxidised by dioxygen to disulfides. The amino acid cysteine may be oxidised to the corresponding disulfide, cystine, in this way.

Biological oxidation of cysteine gives the disulfide cystine. 

Biological oxidation of cysteine can yield, in addition to the disulfide cystine, cysteine sulfinic acid and the sulfonic acid cysteic acid. 

Only the cysteine showed a deactivation of the catalyst however, its deactivation was not reversible (by water wash of the catalyst), a characteristic of the wheat-derived material (3). Therefore, we concluded that the cysteine deactivation was not analogous to the deactivation caused by wheat millfeed hydrolysates. Although cysteine is identified as a component of wheat protein structures, it is not likely to be found as cysteine in the hydrolysis products. More likely, it would be present as the bridged disulfide, cystine, following the oxidative reactions in the processing. 

SYNS CYSTEINE DISULFIDE CYSTIN (-)-CYSTINE CYSTINE ACID DICYSTEINE P,P -DITHIODIALANINE GELUCYSTINE OXIDIZED 1-CYSTEINE... 

Sulfur was recognised as a common element in proteinaceous material in the early eighteenth century, and the disulfide cystine (1) was probably the first sulfur amino acid to be discovered (Morner, 1899) its structure was elucidated by Friedmann(1903). 

Other possible markers for phosgene exposure may be the reduction of cysteine to its disulfide, cystine, upon exposure to phosgene. This reaction would not be specific to phosgene exposure, however. The formation of the acylated dimer Cys-CO-Cys has been shown in vitro when cysteine is treated with phosgene in solution, and this reaction also occurs in the presence of GSH (Fabrizi et al., 2001). 

Integral membrane proteins are oriented in the membrane. In the plasma membrane, the extracellular part of the protein is often characterized by the presence of O-linked polysaccharide groups and disulfide (cystine) bridges... 

Cal Kulis and other patients with cystinuria have a genetically determined defect in the transport of cystine and the basic amino acids, lysine, arginine, and ornithine, across the brush-border membranes of cells in both their small intestine and renal tubules. However, they do not appear to have any symptoms of amino acid deficiency, in part because the amino acids cysteine (which is oxidized in blood and urine to form the disulfide cystine) and arginine can be synthesized in the body (i.e., they are "nonessential" amino acids). Ornithine (an amino acid that is not found in proteins but serves as an intermediate of the urea cycle) can also be synthesized. The most serious problem for these patients is the insolubility of cystine, which can form kidney stones that may lodge in the ureter, causing bleeding and severe pain. 

Ilie clinical aiqylications of this amuoach are best represented in a study by Sampson ef cd. (1985) of measurement of the urinary disulfides cystine and cystdnyl-penicillamine in cystinuria patients. In order to diagnose this disease and monitor patient treatnient, it is necessary to monitor the relatively insoluble disulfides responsible for formation of these urinary tract calculi. Urine samples were simply deproteinized with sulfosalicyclic acid and diluted before injection. For patients treated with penicillamine to increase disulfide solubility in the renal tract, the cysteine-penicillamine... 

Synonyms Cysteine disulfide Cystin Cystine (INCI) Cystine acid Di(a-amino-P-thiolpropionic acid)... 

Recent studies (Friedman et al., 1982 a,b,c 1984) showed that the presence of cysteine or N-acetylcysteine during treatment of at 45, 65, and 75°C increased the protein efficiency ratio (PER) of soy flour. The treated flours had a lower SH content and a higher disulfide (cystine) content than the starting material. These results confirm the described mechanistic hypotheses. 

Sulfhydryl-Disidfide Interconversion. Cysteine is readily oxidized to the disulfide, cystine. This oxidation is catalyzed very efficiently by traces HjC—SH HS—CHj H2C—S—S—CH2... 

Photoprocesses between protein side chains and solvent molecules must also be considered. Although many side chains may have a very low extinction coefficient at the exciting wavelength, some compensation may be achieved if the quantum yield for reaction is relatively high. For example, the disulfide cystine is known to be relatively photoactive when irradiated at 254 nm, particularly because of its significant quantum yield for reaction. ... 

All types of cystinosis are inherited in an autosomal recessive manner. The chromosomal localization was assigned to chromosome 17p. The gene identified encodes a lysosomal membrane protein called cystinosin which is responsible for the transport of the disulfide cystine out of the lysosomal space into the cytosol. A defect of this lysosomal membrane transporter causes cystinosis. The 3 subtypes have been found to be allelic. 

Cysteine is readily converted to the corresponding disulfide, cystine, even under mild oxidative conditions, such as treatment with I2 or potassium hexacyanoferrate (III). Reduction of cystine to cysteine is possible using sodium borohydride or thiol reagents (mercaptoethanol, dithiothreitol) ... 

The sulfur atom (with its polarizable or elastic electron cloud) is one of the best nucleophiles known and cysteine, like serine, can participate in a number of biochemical reations. Also, the sulfhydryl of cysteine is quite oxidizable to give rise to the disulfide, cystine. Another sulfur-containing amino acid is ... 

The oxidation of taurine involves several steps, which we will not discuss here the disulfide cystine can also be oxidized in a similar manner. 

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