Methionine taurine

Cystathionine, methionine, and taurine are not detected by this assay. In addition, this assay may be helpful for the detection of heterozygotes of cystinuria types 2 and 3. 

A CSF sample was analyzed 11-fold. The within-run variation coefficient ranged from 1 to 3.5% with two exceptions tryptophan (5%) and methionine (7%), which partially coeluted. The interassay coefficients of variation were calculated from a series of 11 analyses over a 7-month period. The median CV was 8% only taurine, arginine, and glutamate had CVs slightly in excess of 10%. The recovery of added amino acids to three CSF samples ranged form 83% (taurine) to 101% (isoleucine). Most recoveries were between 90 and 100%. At the lower end of the concentration range for CSF, a level of 1 pmol/1 can be safely detected. 

Age does not have a major influence on amino acid levels, with exception of the neonatal period. Premature babies may have underdeveloped hepatic and renal function, leading to increased tyrosine and methionine in their plasma as well as enhanced urinary losses of cystine, lysine, glycine, proline, hydroxyproline, and cystathionine. Taurine levels are generally increased in the first days of life. 

Homocysteine (Hey) metabolism is closely linked to that of the essential amino acid methionine and thus plays a central role in several vital biological processes. Methionine itself is needed for protein synthesis and donates methyl groups for the synthesis of a broad range of vital methylated compounds. It is also a main source of sulphur and acts as the precursor for several other sulphur-containing amino acids such as cystathionine, cysteine and taurine. In addition, it donates the carbon skeleton for polyamine synthesis [1,2]. Hey is also important in the metabolism of folate and in the breakdown of choline. Hey levels are determined by its synthesis from methionine, which involves several enzymes, its remethylation to methionine and its breakdown by trans-sulphuration. 

Aminoacids and thiols Taurine, L-arginine, histidine, glycine, cysteine glutamine, methionine, /V-acetyl cysteine, TAdenosyl-L-methionine... 

Flavor notes of products of amino compounds-sugars reaction were reviewed with emphasis on amino-ribose system. Meat-like flavor was imparted by browning reaction products of camosine-, citrul-line-, histidine-, glutamic-, 2-pyrrolidone-5-carboxylic-, methionine-, cysteine-, cysteic-, and taurine-ribose. Recent advancements in nitrogen-, oxygen- and sulfur hetercyclics and lipid browning were presented. 

Cysteine is considered a nonessential nutrient because it can be synthesized from methionine via the transsulfuration pathway (Figs. 21-1 and 21-2). Production of cysteine is metabolically important because it serves as a source of sulfur for incorporation into proteins and detoxification reactions. A lack of cysteine needed for incorporation into the structural protein collagen may be responsible for the musculoskeletal abnormalities seen in patients with CBS deficiency. A major metabolic use of cysteine is in the production of glutathionine (y-glutamylcysteinylglycine), an important antioxidant. Another important pathway for cysteine metabolism is its oxidation to cysteinesulfinate, which serves as a precursor for taurine, an amino acid that stabilizes cell membranes in the brain. 

Taurine was discovered in 1827 in ox hUe, where it is conjugated with the bile acids. It was later shown to be a major excretory product of the sulfur amino acids methionine and cysteine. Until about 1976, it was assumed that it was a metabolic end-product whose only function was the conjugation of bile acids. In the rat, taurine synthesis accounts for 70% to 85% of total cysteine catabolism. 

Taurine is a dietary essential in the cat, which is an obligate carnivore with a limited capacity for taurine synthesis from cysteine. On a taurine-free diet, neither supplementary methionine nor cysteine will maintain normal plasma concentrations of taurine, because cats have an alternative pathway of cysteine metabolism reaction with mevalonic acid to yield felinine (3-hydroxy-1,1-dimethylpropyl-cysteine), which is excreted in the urine. The activity of cysteine sulfinic acid decarboxylase in cat liver is very low. 

It is not known to what extent taurine may be a dietary essential for human beings. There is little cysteine sulfinic acid decarboxylase activity in the human liver and, like the cat, loading doses of methionine and cysteine do not result in any significant increase in plasma taurine. This may be because cysteine sulfinic acid can also undergo transamination to /3-sulfhydryl pyruvate, which then loses sulfur dioxide nonenzymically to form pyruvate, thus regulating the amount of taurine that is formed from cysteine. There is no evidence of the development of any taurine deficiency disease under normal conditions. 

Some of these protective substances are found in the diet, such as the vitamins, the sulphur-containing amino acid taurine, and methionine which is an important precursor of proteaive thiols. The sulphur amino acids are found especially in foodstuffs containing protein and, in the case of taurine, only in meat and fish. Vegans and vegetarians are therefore deficient in this important substance. 

Sulfite oxidase catalyzes one of the final stops in the oxidation of the sulfur amino acids. The catabolism of methionine can result in the appearance of its sulfur atom in cysteine, as shown in Chapter 8. Cysteine can be oxidized to cysteine sulfonate, as shciwn in the section on taurine in Chapter 2, and then degraded to pyruvate. Daily, an average of 25 mmol of sulfite is produced in the body. This amount is large compared with the dally intake of fo< sulfite, which is about 2.5 mmol- The point at which sulfite oxidase occurs in the cysteine catabolic pathway is shown in Figure 10,53, Sulfate (SO ") is required for the synthesis of su I fated polypeptides and polysaccharides. It is thought that sulfate is not required in the dict-... 

Methionine produces cystine and taurine breaks down fats reduces blood cholesterol detoxifies the liver is an antioxidant and protects hair, skin, and nails. It is needed for synthesis of RNA and DNA and it assists in the breakdown of niacin, histamine, and adrenalin. It binds to heavy metals, such as lead and cadmium, and carries them out of the body. 

Children do not grow normally if they lack taurine, arge-nine, and cystine. Older children and adults can make cystine from the amino acid methionine. 

Premasol (Cl intec) nonessential amino acids with lower concentrations of methionine, phenylalanine, and glycine these solutions also contain taurine, glutamate, and aspartate... 

This paper (S4) compares the two silylating reagents bis (trimethyl-silyl) acetamide (BSA), first described by Klebe et ad. (K6), and bis-(trimethylsilyl) trifluoroacetamide (BSTFA), for the preparation of volatile trimethylsilyl (TMS) derivatives of 12 sulfur-containing amino acids. BSTFA was recommended as the reagent of choice for taurine, cysteic acid, homocystine, djenkolic acid, ethionine, methionine sulfone, L-2-thiolhistidine, cysteine, and cystine. For S-methyl-L-cysteine, methionine sulfoxide, and methionine, BSA was used as silylating reagent. 

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