Methionine protein-bound

The formation of methionine sulfoxide was observed in connection with hpid peroxidation, phenol oxidation and light exposure in the presence of oxygen and sensitizers such as riboflavin. After in vivo reduction to methionine, protein-bound methionine sulfoxide is apparently biologically available. 

Some chlorinated solvents previously used for the extraction of fats, reacted with proteins with the formation of toxic products. For example, soybean meal extracted with trichloroethylene caused, when fed to calves, aplastic anaemia (a condition that occurs when the body does not produce enough new blood cells) caused by toxic (Z)- and (E)-isomers of S-(l,2-dichlorovinyl)-L-cysteine (11-80), which arises as a reaction product of protein-bound cysteine with trichloroethylene and subsequent proteolysis. The reaction of 1,2-dichloroethane with proteins in cod fillets did not lead to chlorinated reaction products, but the nutritional value was reduced due to the formation of non-utiKsable cysteine, histidine and methionine. Protein-bound cysteine yields, for example, S,S -ethylenebiscysteine (11-81), which is resistant to proteolysis. 

Numerous studies have shown that protein-bound cis-Pt cannot be released by STS (76, 128, 129, 143) (Fig. 9), although STS is able to break the Pt—S bond of the methionine type in the model system (Table III) (131). Therefore, this model system, does not mimic enzymes in every detail for the reaction with STS. This difference might originate from the 2 charge of STS compared to the 1 charge in Naddtc (129), keeping STS more separated from the active site. 

Cytochrome c552 from Euglena gracilis (also known as cytochrome / or c6) contains 87 amino acid residues, two hemes and one flavin per molecule.693 NMR studies706 indicate that the chirality of the axial methionine is similar to that of cytochrome c but different from cytochrome c5Sl. Rapid intramolecular transport has been demonstrated by the use of pulsed laser excitation, and the measurement of reduction kinetics. Both flavin and heme groups are reduced simultaneously on a multisecond time scale, with the transient formation of a protein-bound flavin anion radical.707... 

STS was shown to provide protection from nephrotoxicity when administered in a period between 1 h prior to and 0.5 h after cisplatin injection [36] [37]. It has been shown that protein-bound cisplatin cannot be released by STS [38] [39][40], although STS is able to break the Pt-thioether bond in methionine model systems [41], A likely explanation for its protecting effect is that STS is known to be concentrated extensively in the kidney, where... 

Nutrition Effect of Protein-Bound Methionine Sulfoxide. There is some discrepancy in the results concerning the biological availability of protein-bound methionine sulfoxide. Ellinger and Palmer (71) found that oxidized casein had a lower NPU (Net Protein Utilization) than normal casein. Slump and Schreuder (72) concluded that there was a positive biological availability of peptide-bound methionine sulfoxide. 

This reaction is catalyzed by manganese ions at pH values from 6 to 7.5. S02 can also react with cystine to yield a series of oxidation products. Some of the possible reaction products resulting from the oxidation of sulfur amino acids are listed in Table 3-11. Nielsen et al. (1985) studied the reactions between protein-bound amino acids and oxidizing lipids. Significant losses occurred of the amino acids lysine, tryptophan, and histidine. Methionine was extensively oxidized to its sulfoxide. Increasing water activity increased losses of lysine and tryptophan but had no effect on methionine oxidation. 

Sharov, V. S., Ferrington, D. A., Squier, T. C., and Schoneich, C., Diastereoselective reduction of protein-bound methionine sulfoxide by methionine sulfoxide reductase. FEBS Lett. 455, 247-250(1999). 

Mammalia contain two methionine sulfoxide reductases, forms A and B. Methionine sulfoxide reductase B is a selenoprotein, which reduces the R form of free or protein-bound methionine sulfoxides to methionine with thioredoxin as the reductant. Together with isoform A (which does not contain selenium), the enzyme can repair oxidatively damaged protein and thus contributes to the antioxidant system of the cell. ... 

Figure 31.13. DNA Recognition Through p Strands. The structure of the methionine repressor bound to DNA reveals that residues in P strands, rather than a helices, participate in the crucial interactions between the protein and...

After intravenous administration of oxaliplatin, about 33% and 40% of the dose is bound to erythrocytes and plasma proteins. The half-life averages 26 days, which is in accordance with the normal life expectancy of erythrocytes (12-50 days). Oxaliplatin undergoes rapid non-enzymatic biotransformation to form a variety of reactive platinum intermediates, which bind rapidly and extensively to plasma proteins and erythrocytes. The antineoplastic and toxic properties appear to reside in the non-protein bound fraction, whereas platinum bound to plasma proteins or erythrocytes is considered to be pharmacologically inactive. Biotransformation produces DACH-platinum dichloride, 12-DACH-platinum dicysteinate, 1,2-DACH-platinum diglutathionate, 1,2-DACH-platinum mono-glutathionate, and 1,2-DACH-platinum methionine. The erythrocyte contains only thiol derivatives, whereas all derivatives can be recovered from the plasma. 

Furthermore, based on earlier calculations (39) for the type 1 copper protein plastocyanin, ligand-field parameters for the blue copper in laccase have been derived. These reports (37,38) also include a structural representation of the type 1 center composed of a flattened tetrahedron (D2d symmetry) with two imidazole side-chains, a cysteine sulfur, and a fourth ligand (which probably is methionine sulfur), bound to the metal ion. Although no such low-temperature experiments have been performed with ascorbate oxidase, one might anticipate similar structural features for the blue type 1 centers. 

Carnitine is synthesized from two essential amino acids, lysine and methionine. S-Adenosylmethionine donates three methyl groups to a lysyl residue of a protein with the formation of a protein-bound trimethyllysyl. Proteolysis yields trimethyllysine, which is converted to carnitine (Figure 18-2). In humans, liver and kidney are major sites of carnitine production from there it is transported to skeletal and cardiac muscle, where it cannot be synthesized. 

Fig. 3A, B Protein repair mechanisms. Panel A demonstrates the oxidation of thiol groups, leading to the formation of an intermolecular cross-link. This modification can be repaired by two mechanisms, one involving gluathione and the other thioredoxin. Panel B demonstrates the methionine oxidation,leading to methionine sulfoxide and methionine sulfone. Methionine sulfoxide can be repaired either in its protein-bound or soluble form by two types of enzymes (1 and 11). For more detailed description see the text...

A large body of literature exists concerning the measurement of protein oxidation during aging in different models. Most of the studies measure the formation of protein-bound carbonyls [88-108]. Other authors suggested or used other amino acid modifications, like tyrosine oxidation products such as dityrosine, o-tyrosine or nitrotyrosine [109-112], the formation of 5-hydroxyl-2-amino valeric acid [ 113], or methionine sulfoxide formation [112]. Changes... 

Oxidation of proteins. ROS can directly oxidize free or protein-bound amino acids, leading to deactivation of enzymes (Stadtman, 1990 Stadtman and Oliver, 1991 Stadtman and Berlett, 1991). Cysteine, methionine, histidine and tryptophan are preferentially oxidized, resulting in sulfenic, sulfinic or sulfonic acids from thio-containing amino acids and in histidine- and tryptophan-endoperoxides, which subsequently degrade (Sies,... 

Because a colorimetric screening test for urinary homocystine was positive, the doctor ordered several biochemical studies on Homer Sistine s serum, which included tests for methionine, homocyst(e)ine (both free and protein-bound), cystine, vitamin B12, and folate. The level of homocystine in a 24-hour urine collection was also measured. 

The results were as follows the serum methionine level was 980 p,M (reference range, <30) serum homocyst(e)ine (both free and protein bound) was markedly elevated cystine was not detected in the serum the serum B12 and folate levels were normal. A 24-hour urine homocystine level was elevated. 

Both acetylated and nonacetylated adducts have been isolated from hepatic macromolecules of rats treated with AAF or N-hydroxy-AAF. Methionine adducts represent about 10% of protein-bound... 

The main form of selenium in most foods is protein-bound seleno-methionine. Supplements of selenium are provided by mineral salts containing sodium selenite, slow-release capsules and selenium-enriched yeast. 

Proteins and their derivatives, especially the lectins, extracellular to the cell wall, are now a common observation (Tables 5.1.1 and 5.1.2). Lectins from the bark of black locust (Robinia pseudoacacia) have been isolated by specific absorption on formaldehyde-fixed human erythrocytes and eluted with a borate solution (68). The lectin is homogeneous on disc electrophoresis and yields three bands on isoelectric focusing. It has a molecular weight of s 110000 and consists of two subunits (MW 29000 and 31500). Its pi is 5.9 and it contains large amounts of aspartic acid, threonine, and serine, no cysteine, and very little methionine. Covalently bound neutral sugar constitutes 7.2% of the structure and glucosamine constitutes 0.47%. 

An oxidation of food proteins leads partially to changes in the nutritional and functional properties and the sulfur amino acids methionine and cystein as well as histidine, tyrosine and tryptophan are susceptible to oxidation even under relatively mild conditions. Protein-bound forms of these amino acids can also be oxidized under conditions that sometimes prevail in stored food. 

---