Cystine Friedmann

The actual formation of pyruvic acid from various mercapturic acids upon which these formulae for cysteine and cystine were founded, was only shown later by Baumann s pupils, Konigs, Brenzinger and Schmitz, and in conjunction with Suter s observation that a-thiolactic acid was formed by the hydrolysis of horn, this formula for cystine was accepted. The results obtained, however, scarcely justified this formula as pointed out by Friedmann in 1902, who showed conclusively that the cystine, obtained from proteins, had not this constitution. 

By oxidising cystine with bromine water, Friedmann obtained cysteic acid, i.e., either... 

The synthesis of cystine by Erlenmeyer jun. in 1903, which was more fully described by him and Storp in 1904, showed that Friedmann s formula was correct —... 

The formation of bromophenylmercapturic acid from bromobenzene and cystine in the organism, if it had the formula given it by Baumann now seemed scarcely possible, unless an isomeric a-thio-y8-aminopropionic acid were also present in the protein molecule together with the di-/8-thio-a-aminopropionic acid or cystine. The investigation of their constitution was therefore taken up by Friedmann in 1904, who succeeded in showing that they were also derived from -thio-a-aminopropionic acid and not from the isomeric a-thio-/8-aminopropionic acid. 

It was first observed by Suter, in 1895, that a-thiolactic acid was formed by the hydrolysis of proteins, and it was constantly obtained by Friedmann. It was always regarded as a secondary product, but its formation from cystine could not be explained, as cystine is a /3-thiopro-pionic acid. 

Fischer and Suzuki soon afterwards showed that Neuberg and Mayer s stone cystine contained tyrosine, and that its different behaviour to protein cystine was due to the presence of this compound. Rothera also could find no difference between stone cystine and protein cystine, and further, Gabriel s synthesis of isocysteine or a-thio-/8-aminopropionic acid and isocystine, which had quite different properties to cystine, though the two were much alike in many of their reactions, proved that stone cystine and protein cystine must be identical substances. Finally, it has been shown by Friedmann that a-thiolactic acid, ammonia PT. I. 4... 

Thus, the work of Friedmann on the constitution of cystine, its synthesis by Erlenmeyer jun. and by Fischer, definitely show that it has the composition... 

Sulfur was recognised as a common element in proteinaceous material in the early eighteenth century, and the disulfide cystine (1) was probably the first sulfur amino acid to be discovered (Morner, 1899) its structure was elucidated by Friedmann(1903). 

Occurs normally in the outer part of the sheep s fleece, where the wool is exposed to light and weather Martin, Synge, Advances in Protein Chemistry 2, 3 (1945). Prepd from cystine or cysteine by oxidation with bromine in water Friedmann, Beitrdge zur Chemischen Physiologic tmd Pathologie 3, 25, 38 Gortner, Hoffman, J. Biol Chem. 72, 435 (1927). 

Cystine, as main component of bladder (gr. Kystis) stone, isolated by Wollaston obtained from protein hydrolyzate only in 1899 by K.A.H. Morner. Reduction yields cysteine E. Baumann, 1884. Structure E. Friedmann 1903. Synthesis E. Erlenmeyer, 1903. 

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