Tyrosinate

As constituents of proteins the amino-acids are important constituents of the food of animals. Certain amino-acids can be made in the body from ammonia and non-nitrogenous sources others can be made from other amino-acids, e.g. tyrosine from phenylalanine and cystine from methionine, but many are essential ingredients of the diet. The list of essential amino-acids depends partly on the species. See also peptides and proteins. 

CgHiiNO. M.p. 282 C (decomp.). The naturally occurring substance is laevorotatory. It is an amino-acid isolated from various plant sources, but not found in the animal body. It is formed from tyrosine as the first stage in the oxidation of tyrosine to melanin. It is used in the treatment of Parkinson s disease. 

C. Excreted in the urine in the rare hereditary disease alkaptonuria. Homogentisic acid is easily oxidized in the air to dark-coloured polymeric products, so that urine from patients with alkaptonuria turns gradually black. It is formed from tyrosine and is an intermediate in tyrosine breakdown in the body. Alkaptonuria is due to the absence of the liver enzyme which cleaves the aromatic ring. 

First, it is possible to excite a chromophore corresponding to the active site, and detennine which modes interact with it. Second, by using UV excitation, the amino acids with phenyl rings (tryptophan and tyrosine, and a small contribution from phenylalanine) can be selectively excited [4], The frequency shifts in the resonance Raman spectrum associated with them provide infomiation on their enviromnent. 

The last part of this account will be devoted to protein kinases and protein phosphatases and some recent results we have obtained for them. Protein kinases and phosphatases are signaling biomolecules that control the level of phosphorylation and dephosphorylation of tyrosine, serine or threonine residues in other proteins, and by this means regulate a variety of fundamental cellular processes including cell growth and proliferation, cell cycle and cytoskeletal integrity. 

Zhang, Z.-Y., Dixon, J. E. Active site labeling of the yersinia protein tyrosine phosphatase The determination of the pKa of active site cysteine and the function of the conserved histidine 402. Biochem. 32 (1993) 9340-9345. 

Zhang and co-workers worked on the structure-based, computer-assisted search for low molecular weight, non-peptidic protein tyrosine phosphate IB (PTPIB) inhibitors, also using the DOCK methodology [89], They identified several potent and selective PTPIB inhibitors by saeening the ACD. 

A) Amino-aliphatic carboxylic acids. Glycine, tyrosine cystine. ... 

Tyrosine and cystine have been included primarily for students of biochemistry, physiology and medicine these two amino-acids might, however, be omitted by other students. 

Glycine or amino-acetic acid, NHjCHjCOOH tyrosine, />-HOC<.H4CH2CH(NH2)COOH cystine, [ SCH2CH(NH2)COOH]2. 

A) AMINO-ALIPHATIC CARBOXYLIC ACIDS. Glycine, tyrosine, cystine. 

Tyrosine and cystine are colourless solids almost insoluble in water gfid in ethanol (tyrosine dissolves in hot water). They are readily soluble in dilute caustic alkali solution, in ammonia and mineral acids, but not in acetic acid. They are also classed as neutral ampholytes. ... 

Tyrosine and cystine are insoluble in water therefore place about 0 2 g. in the test-tube A, dissolve in the dil. NaOH solution, add phenolphthalein as before and then add dil. HCl until pink colour is iust not discharged then proceed as above. 

Many amino-acjds are easily identified as their 3,5-dinitroben2oyl derivatives (Saunders, Biochem. Jour., 1934, 28, 580 1942, 36, 368). Cystine, however, forms a gelatinous derivative, but is readily identified by special tests. Tyrosine does not form a derivative under these conditions. 

Mercuric nitrite reaction (Millon s reaction). Dissolve a very small crystal of tyrosine in i ml. of water, add 1-2 drops of mercuric nitrate solution, and I drop of dil. HjSO, and then boil. Cool, add i drop of sodium nitrite solution and warm again a red coloration is obtained. 

Formalin coloration. To a small crystal of tyrosine, add 1 drop of 40% formalin, 1 ml. of water, and i ml. of cone. H2SO4. Boil gently a deep green coloration is developed. 

Almost insoluble in cold water. Higher alcohols (including benzyl alcohol), higher phenols (e.g., naphthols), metaformaldehyde, paraldehyde, aromatic aldehydes, higher ketones (including acetophenone), aromatic acids, most esters, ethers, oxamide and domatic amides, sulphonamides, aromatic imides, aromatic nitriles, aromatic acid anhydrides, aromatic acid chlorides, sulphonyl chlorides, starch, aromatic amines, anilides, tyrosine, cystine, nitrocompounds, uric acid, halogeno-hydrocarbons, hydrocarbons. 

Procedure. The method can be tested using the matrix of concentrations, in micromoles per liter (pmol L ), of tryptophan and tyrosine at 280 nrrr suitably rrrodified to take into account constant absorption at 280 nrrr of some absorber that is neither tryptophan nor tyrosine... 

With phenylalanine and tyrosine, the sodium salt of the derivative is sparingly soluble in water and separates during the initial reaction. Acidify the suspension to Congo red the salts pass into solution and the mixture separates into two layers. The derivative is in the etheresil lay and crystallises from it within a few minutes. It is filtered off and recrystaUised. 

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