Cystine taurine

The linearity of the AAA was tested with an aqueous mixture. In general the assay was linear up to 2500 pmol/1, for glutamine even 5000 pmol/1. Some amino acids were tested at a lower level (cystine, taurine, citrulline) and were found to be linear up to 625-1250 pmol/1. 

Cystine) Taurine Bile acid conjugation, neuronal cell undernutrition, inflammatory diseases Reduces contrast-induced nephropathy in... 

These reactions also showed how taurine might originate in the body from cystine. 

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. 

Cystinuria has been known for a long time (A2, H18, Yl), but it was Dent and Rose (D12) who noticed, in 15 patients suffering from cystine caleulosis, that cystine was not the only amino acid abnormally abundantly excreted by the kidney. They observed that arginine and lysine were also excreted in abnormally large amounts, and Stein (S31) reported this to be true of ornithine as well. Bickel refers to the condition by using the expression lysine cystinuria, but this is in fact misleading because it infers that these are the only two amino acids concerned, whereas that is not the case. Taurine excretion, on the other hand, is low (S31). The cystine plasma level is either normal or low (D19, Fll). 

A thorough investigation of this type of amino aciduria has led to a more accurate and more complete picture of it (S34). Taurine excretion is low proline, citrulline, and cystine excretion may be abnormally high, and when this is the case there does not seem to be a relation between the cystine output, which may be considerable, and that of lysine. Moreover, whereas the intake of a meal has but little influence on amino aciduria in normals, it has a definite effect on the output of amino acids in the case of Wilson s disease finally the amino acid fasting levels in plasma are at the lower limit of normal. 

Browning of glucose and simple mixtures of amino acids did not produce authentic meaty aromas, but heating a synthetic mixture of all compounds identified in beef extract in the appropriate concentration, including alanine, glutamic acid, asparagine, taurine, carnosine, anserine, histidine, cystine, creatinine, hypoxanthine, lactic and succinic acid, produced a highly desirable meaty odor. 

As already pointed out, cysteine may be metabolized to pyruvate, or it can be oxidized to cystine. It can also be converted to taurine, NH3+-CH2-CH2-S03. Taurine is obtained by oxidizing the -SH group of cysteine and losing the carboxyl group of decarboxylation. Taurine is quite abundant in most tissues and is said to be the most abundant "amino acid" of the human organism. One of its functions is to conjugate primary bile acids (Chapter 19). 

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. 

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. 

Cysteine is a sulfur-containing amino acid. Cysteine is a precursor of mercaptoethanolamine, taurine, and sulfate. Cysteine can be reversibly oxidized to form cystine. 

Growing chicken128 and hens129 utilize sulphate sulphur for cystine synthesis. Biological radio-tracer experiments130 with Na235S04 (10 fiCi) have shown that over 65% of the 35S administered to a 24-hour-old embryo is incorporated into taurine of the chick. No radioactive cystine, methionine or cysteic acid was detected in the hydrolysate obtained from the embryo and only a small portion of total taurine-35S occurs as taurocholic acid. The embryo is unable to utilize sulphate sulphur for cystine synthesis. 

Incubation of embrionic calf liver with 35S-labelled sodium sulphite, sodium pyruvate and sodium glutamate at 38 °C under nitrogen resulted in formation of 35S-cysteinesulphinic acid133,134. 35S-hypotaurine has also been isolated, but taurine-35S and cystine-35S have not been found. In the presence of serine, the yield of 35S-cysteinesulphinic acid was smaller. Organic 35S compounds without amino groups have also been formed in the same experiment. In the conditions employed in this bioexperiment cysteinesulphinic acid is not reduced to cystine-3 5S, although such reduction was found possible in vivo. 

The [3 5S] cysteinesulphinic acid, included in the scheme in equation 81, has been identified unambiguously by Chapeville and Fromageot149 in the liver and kidney of seven-week-old rats injected with [35S]cystine hydrochloride and sacrified 15 minutes later. [35S]Taurine and [35S]sulphate have also been detected, and the [35S]cysteinesulphinic acid has been oxidized subsequently by performic acid to [35S]cysteic acid. 

The aerobic metabolism of cystine-3 5S by chicken embryo, investigated166 both in vivo and in vitro, resulted in the formation of cystinedisulphoxide-35S (in vitro only), [35S] cystinesulphinic acid, [35S] cysteic acid, [35S]taurine and sulphate-35S. Hypotaurine has been detected neither in vivo nor in vitro. This indicates that, contrary to what had been observed in mammalian liver, hypotaurine is not the precursor of taurine in chicken embryo (equation 86). The enzyme decarboxylase, which effectively decarboxylates [35S]cysteic acid, does not act on cysteinesulphinic acid. Sulphate-35S may be produced also by the desulphination of cysteinesulphinic acid (equation 87) or from some other... 

Chick embryo utilizes 35S-sulphate for the synthesis of 35S-taurine, but the amount of sulphate-sulphur present in the unincubated egg is insufficient to furnish S necessary for the taurine synthesized. Injection167 of L-methionine-35S or of L-cysteine HCl-35S into the egg white, and determination of the distribution of 35S in the chick hatched from the incubated egg revealed that with [35S]cysteine 10% of the administered 35S is located in the chick as taurine, 12% as sulphate, 1.3% as methionine and 49% as cystine. With methionine-35S 9.1% was recovered as taurine, 10% as sulphate, 43% as cystine and 35% as methionine. These findings indicate that methionine is converted to cystine during embryonic development, but significant amounts of cysteine-35S were incorporated also into methionine. Possibly, trans-sulphonation from methionine to cysteine is reversible to some extent in the chick embryo, similarly to what has been found in young rats168. 

The more complex sulphur requirements of the marine animals are met largely by cysteine, cystine, methionine, biotin, and thiamine (Young and Maw, 1958) (Fig. 4). Cysteine is a component of the tripeptide glutathione and a precursor of taurine. Methionine is as an essential amino acid involved in biosynthesis of proteins, creatine and adrenaline. Adenosylmethionine is considered to be the active part in transmethylation, e.g. of choline. Methionine is part of the pathways to homocysteine, cystathionine and methylthioadenosine (Young and Maw, 1958). Various organisms convert cysteine and/or cystine into mercapturic acids, cysteine sulphinic acid, and thiazolidine derivatives (Zobell, 1963). 

Oxidation of Cystine, Cystine has been reported to initiate a series of reactions in which the S—S bond remains intact. An oxidation product is cystine disulfoxide, RSOSOR. This compound can yield both cysteine and sulfate in the intact rat, but most of it is converted to taurine. Both carboxyl groups of cystine disulfoxide are removed by a decarboxylase different from cysteic decarboxylase. Oxidation and hydrolysis of the decarboxylation product would yield two equivalents of taurine, but the individual steps of this conversion have not been isolated. 

Another metabolic pathway directly from cystine which yields taurine has been proposed by Medes and co-workers. The steps involved are given in reactions 9 to 12 of Fig. 2. The initial oxidation product, cystine disulfoxide, is readily oxidized to sulfate in the animal organism. The oxidation step from cystine to the disulfoxide appears to be reversible, as Bennett found that this compound was capable of replacing cystine in the diet of the rat in equimolar amounts. Decarboxylation of cystine disulfoxide was deduced from the active decarboxylation of cystine with the simultaneous absorption of O2 by an enzyme present in liver brei. 

Tests to determine the nature of the compounds formed from the decarboxylation of cystine that could undergo oxidation led to the observation that cystamine disulfoxide was oxidized with ease, whereas cystamine was completely resistant. From these observations, it was hypothesized that two oxidizing enzymes may be involved in the reaction, one oxidizing cystine to the disulfoxide, and one continuing the oxidation of the cystamine disulfoxide subsequent to the decarboxylation of the cystine disulfoxide. If it is assumed that the cystamine disulfoxide is simultaneously oxidized and cleaved to 2-aminoethanesulfinic acid, the oxidation scheme leads to the intermediate that was established for the biosynthesis of taurine from cysteine by Awapara. ... 

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