Amino acids sulphur-containing

M.p. 283 C (decomp.). Soluble in water and alcohol. The naturally occurring substance is laevorotatory. Methionine is one of the natural sulphur-containing amino-acids, and is present in small quantities in the hydrolysis pro-... 

Protamines. Strongly basic, low mol. wt. proteins which contain high levels of arginine, but no sulphur-containing amino-acids. They are soluble proteins, associated with nucleic acids and are obtained in large quantity from fish spermatozoa. 

Name three sulphur containing amino acids. 

Metal complexes of sulphur-containing amino-acids. C, A. McAuliffe and S. G. Murray, Inorg. Chim. Acta, Rev., 1972, 5,103-121 (190). 

Redox reactions of sulphur-containing amino-acid residues in proteins and metalloproteins. 

Weser U (1985) Redox Reactions of Sulphur-Containing Amino-Acid Residues in Proteins and Metalloproteins, an XPS Study. 61 145-160 Weser U (1973) Structural Aspects and Biochemical Function of Erythrocuprein. 17 1-65 Weser U, see Abolmaali B (1998) 91 91-190... 

Salmonella typhi, in the presence of glucose, reduces bismuth sulphite to bismuth sulphide, a black compound the organism can produce hydrogen sulphide from sulphur-containing amino acids in the medium and this will react with ferrous ions to give a black deposit of ferrous sulphide (Table 1.2). 

The results obtained with this procedure are similar to those previously reported in the literature by Hangartner, Hagenguth et al and Zeman et al (4, 2, 5, 6). The major exception, being the complete lack of alkylated pyrazines and alkylated thiophenes. These odour-intensive compounds arise from the thermal decomposition of proteins and sulphur containing amino acids. They also develop in the thermally induced reaction of proteins with carbohydrates (Maillard reaction). The authors indicated above have demonstrated that these compounds are invariably produced during the thermal treatment of sludge, a process which is not used in this Authority. 

Redox Reactions of Sulphur-Containing Amino-Acid Residues in Proteins and Metalloproteins, an XPS Study... 

Redox Reactions of Sulphur-Containing Amino-Acid Residues... 

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. 

Casein is low in sulphur (0.8%) while the whey proteins are relatively rich (1.7%). Differences in sulphur content become more apparent if one considers the levels of individual sulphur-containing amino acids. The sulphur of casein is present mainly in methionine, with low concentrations of cysteine and cystine in fact the principal caseins contain only methionine. The whey proteins contain significant amounts of both cysteine and cystine in addition to methionine and these amino acids are responsible, in part, for many of the changes which occur in milk on heating, e.g. cooked flavour, increased rennet coagulation time (due to interaction between /Mactoglobulin and K-casein) and improved heat stability of milk pre-heated prior to sterilization. 

The amino acid composition of keratin, the protein of hair and wool, includes a greater-than-average proportion of the sulphur-containing amino acid, cystine. Since this is the least soluble of the protein amino acids it can readily be isolated after carefully neutralising an acid hydrolysate of hair (Expt 5.187). Protein hydrolysis is usually effected by boiling for about 10-20 hours with 20 per cent hydrochloric acid. The hydrolysis of hair for the isolation of cystine is, however, best achieved using a mixture of hydrochloric and formic acids. 

The changes in PCD potential for enzymatic bath, shown in Fig. 4, correspond well with the results obtained by the HPLC method (Fig. 6). In the enzymatic bath 18 amino acids were analysed. Aspartic acid, as well as methionine and cysteine, two sulphur containing amino acids showed increased concentrations (Fig. 6). 

Sulphur-containing amino acids can be converted into derivatives after prior esterification with HC1—methanol by the same procedure. 

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. 

The cyanide in cassava that is not properly prepared can be released by the action of enzymes in our gut and can poison an individual. It does this by binding to an enzyme in the mitochondria inside the cell which blocks the production of energy. In vulnerable tissues, like the nerves of the spinal cord, this causes damage. The detoxication of cyanide with sulphur, derived from sulphur-containing amino acids in protein, produces thiocyanate, which is excreted into the urine, but this system is easily overwhelmed especially in those deficient in sulphur. Drought and poor soil seem to increase the production of linamarin in cassava, and it is possible that other dietary deficiencies may contribute to the nerve damage. 

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