Sulphur amino acids

Heger J, Van Phung T and Krizova L (2002), Efficiency of amino acid utilization in the growing pig at suboptimal levels of intake lysine, threonine, sulphur amino acids and tryptophan , J Anim Physiol An N, 86, 153-165. 

Taurine is a sulphur amino acid, which is not present in protein (see text). For the calculation from the amount in fresh (wet) tissue, e.g. pmol/g fresh tissue, it is assumed that the intracellular water makes up 40% of the weight. 

As a group, the caseins are deficient in sulphur amino acids which limits their biological value (80 egg albumen = 100). asl- and -caseins contain no cysteine or cystine while aa2- and x-caseins have two cysteine residues per mole, which normally exist as intermolecular disulphides. 

Zahn, H. and Gattner, H. G. (1997). Hair sulphur amino acid analysis, in Formation and Structure of Human Hair (P. Jolles, H. Zahn, and H. Hocker, Eds.). Basel Birkhaurser Verlag, 239-258. 

For this reason, the lack of enough BAN can make the yeast use sulphur amino acids (cysteine and methionine), thus releasing hydrogen sulphite and mercaptans. Thus, supplementing with ammonium salts is recommended not only to avoid stuck and sluggish fermentations but also to prevent reduction off-odours (Jiranek etal. 1995). 

ZamboneUi, C., MutineUi, P., Pacchetti, G. (1975) Biosynthesis of sulphur amino acids in Saccharomyces cerevisiae. I. Genetic analysis of leaky mutants of sulphite reductase. Archives of Microbiology, 102, 247-251. 

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. 

Abstract The diet of industrialised countries is usually rich in amino acids, which are partly used as a source of calories. However, metabolic alterations are observed in diseased patients and a preferential retention of Sulphurated Amino Acids (SAA) occurs during the inflammatory response. It has been demonstrated in an acute sepsis phase model in rats that the metabolism of L-Cysteine (Cys) is modified. Glutathione (GSH) concentration is greater in the liver, kidneys and other organs and Cys incorporation into proteins is higher in the spleen and lungs. In the plasma Acute Phase Proteins are released while Albumin is decreased. The pro-inflammatory cytokines such as Interleukin-1, lnterleukin-6 and TNF-a are the main initiators altering protein and amino acid metabolism. 

These changes are induced by a complex intercellular signalling system, whose main constituents are inflammation-associated cytokines. Among other functions. Interleukin-1, Interieukin-6 and Tumour Necrosis Factor-a initiate the alteration of protein and amino acid metabolism designed to support the increased demand of amino acids to sustain the immune response. In particular, lnterleukin-6, stimulates the production of hepatic APP. The relationship with the sulphurated amino acids (SAA) will be discussed in the following chapters. 

However, metabolic alterations are observed under pathological conditions and a preferential retention of sulphur amino acids, evaluated as a urinary sulphur excretion, occurs during an inflammatory response [11-13]. Following a fracture or bums, urinary nitrogen excretion is enhanced to a greater extent than sulphur excretion [14]. Moreover, a... 

Within the liver there will be competition between acute phase protein and GSH synthesis for the cellular sulphur amino acid pool. The question therefore arises whether incorporation of Cysteine into both of these end-products, during the inflammatory response, is influenced equally by alteration in dietary sulphur amino acid intake... An insufficient intake of sulphur amino acids will thereby exert a pro-inflammatory influence... 

J. Martensson, J. Larsson and H. Nordstrom, Amino Acid Metabolism During the Anabolic Phase on Severly Burned Patients w ith Special Reference to Sulphur Amino Acids. Eur J Clinical Invest 17 (1987) 13-15. 

Stress. The information available suggests that stress may increase metabolism of foreign compounds. Diet. The constituents and amount of food (deficiency/starvation) may influence disposition and hence toxicity of chemicals. Food constituents may be enzyme inducers or inhibitors. Lack of food or specific constituents (e.g. protein or vitamins) may decrease metabolic capability, e.g. a protein deficient diet decreases cytochrome P-450 activity. Lack of sulphur amino acids decreases glutathione level. The effect on toxicity will depend on the role of metabolism. 

Tracer experiments126 with Na235S04 added to the diet of chicken have revealed that sodium sulphate improves growth, feed efficiency, and is capable of stimulating normal feather development even when the sulphur amino-acid content in the diet is too low to support optimal growth. About 20% of sulphur from Na235S04 retained by chickens was found to be incorporated into body taurine. 

Metabolism of35S-sulphur amino acids in invertebrates... 

The metabolism of 35S-labelled sulphur amino acids in marine and fresh water invertebrates has been studied and reviewed by Awapara and coworkers179 180. The general conclusion drawn from these studies was that the metabolism of sulphur-bearing amino acids in two molluscs studied is qualitatively the same as in mammals. Taurine, which serves as an osmoregulator in marine molluscs, is formed either by decarboxylation of cysteic acid (in Rangia cuneata) or by oxidation of hypotaurine (in Mytilus edulis), derived from cysteinesulphinic acid by decarboxylation. In Arenicola cristata only the terminal reactions are different. Methionine and cysteine sulphur incorporates into taurocyamine by transamidation between taurine and arginine. 

The amino acid composition of some )S-lg variants is shown in Table 4.4. It is rich in sulphur amino acids which give it a high biological value of 110. It contains 2 moles of cystine and 1 mole of cysteine per monomer of 18 kDa. The cysteine is especially important since it reacts, following heat denatura-tion, with the disulphide of K-casein and significantly affects rennet coagulation and the heat stability properties of milk it is also responsible for the cooked flavour of heated milk. Some /S-lgs, e.g. porcine, do not contain a free sulphydryl group. The isoionic point of bovine j3-lgs is c. pH 5.2. 

Baric 1, Fowler B. Sulphur amino acids. In Nenad B et al., editors. Physician s guide to the diagnosis, treatment, and follow-up of inherited metaboUc diseases. Heidelbeig Springer 2014. p. 43. 

In theory, the antidigestive properties of Pi s combined with the above enzyme-based defenses should provide "double-barrel negative resistance, since the first increases the need for sulphur amino acids, and the second has the potential to decrease the availability of these and other amino acids. However, in order to jointly utilize these two defenses effectively, a deeper knowledge of their chemical interrelationships is necessary. Potential complications in the use of proteinase inhibitors will be discussed below. 

We have described an approach to host plant resistance that involves the use of plant oxidative enzymes to irrevocably deprive the insect of nutrients. We have emphasized that the chemical reactions catalyzed by POD and PPO have the potential to destroy a variety of essential or limiting amino acids (Table X). In particular, these reactions are adept at destroying lysine and cysteine. Integral lysine is necessary for proper enzymatic hydrolysis of protein. Cysteine and methionine, amongst other uses, are required to synthesize trjrpsin. The action of PPO and POD in conjunction with Pi s are proposed to place a severe strain on the insect for high sulphur amino acid intake. This strain may be further exacerbated by the complementary action of quinones... 

Cysteine also donates its sulphur to form homocysteine and eventually the second critical sulphur amino acid, methionine. Methionine is the S-methyl ether of homocysteine, a cysteine analogue with one additional... 

Mercapturic acid production seems to have first call on the sulphur amino acid reserves and serious deficiency states can be induced in rats by hepatotoxic hydrocarbons. Diets high in cysteine and methionine will protect against the liver damage. Some mercapturic acid production may also result from reaction of protein thiol groups with the hydrocarbons, hydrolysis of the protein to the S-substituted cysteine and its N-acylation. However, the vast majority is formed via the glutathione adducts if the hydrocarbon dose is not so great as to deplete the glutathione reserves of the liver. 

Cheeke PR, Gorman GR (1974) Influence of dietary protein and sulphur amino-acid levels on the toxicity of Senecio jacobaea (tansy ragwort) to rats. Nutr Rep Int 9 197-207... 

Molnar-Perl I., Friedman M. Inhibiton of browning by sulphur amino acids. III. Apples and potatoes. Journal of Agricultural and Food Chemistry, 38 1652-1656 (1990). 

N., and Wharton, B. A., 1978, Duodenal bile acid conjugation patterns and dietary sulphur amino acids in the newborn. Gut 19 95. 

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