Dl Methionine

The nutritional value of a proteia can be improved by the addition of amino acids of low abundance ia that proteia. Thus the fortification of plant proteias such as wheat, com, and soybean with L-lysiae, DL-methionine, or other essential amino acids (L-tryptophan and L-threonine) is expected to alleviate some food problems (11). Such fortification has been widespread ia the feedstuff of domestic animals. 

DL-Alanine is the first amino acid which was synthesi2ed chemically (138). Glycine and DL-methionine have also been suppHed by this method (20). However, amino acids formed by the chemical method are racemic, and it is necessary to resolve the mixture to get the L- or D-form amino acid which is usually demanded. 

Chemical Production. Glyciae, DL-methionine, and dl-alanine ate produced by chemical synthesis. From 1964 to 1974, some glutamic acid was produced chemically (48). The synthetic amino acid with the largest production is DL-methionine from actoleia (see Acrolein and derivatives). The iadustrial production method is shown ia the foUowiag (210). 

An estimation of the amount of amino acid production and the production methods are shown ia Table 11. About 340,000 t/yr of L-glutamic acid, principally as its monosodium salt, are manufactured ia the world, about 85% ia the Asian area. The demand for DL-methionine and L-lysiae as feed supplements varies considerably depending on such factors as the soybean harvest ia the United States and the anchovy catch ia Pern. Because of the actions of D-amiao acid oxidase and i.-amino acid transamiaase ia the animal body (156), the D-form of methionine is as equally nutritive as the L-form, so that DL-methionine which is iaexpensively produced by chemical synthesis is primarily used as a feed supplement. In the United States the methionine hydroxy analogue is partially used ia place of methionine. The consumption of L-lysiae has iacreased ia recent years. The world consumption tripled from 35,000 t ia 1982 to 100,000 t ia 1987 (214). Current world consumption of L-tryptophan and i.-threonine are several tens to hundreds of tons. The demand for L-phenylalanine as the raw material for the synthesis of aspartame has been increasing markedly. 

L-methionine DL-methionine + Asp D-amino acid oxidase + transaminase Trigonopsis variabilis ... 

In Industrial Chemicals. Recendy, as some amino acids (eg, L-glutamic acid, L-lysine, glycine, DL-alanine, DL-methionine) have become less expensive chemical materials, they have been employed in various appHcation fields. Poly(amino acid)s are attracting attention as biodegradable polymers in connection with environmental protection (236). 

The mixture of D and L optical forms of this hydroxy analogue of methionine is converted to the calcium salt which is used in animal feed supplements. Cyanohydrins react with ammonium carbonate to form hydantoins (2), which yield amino acids upon hydrolysis. Commercial DL-methionine [59-57-8] is produced by hydrolysis of the hydantoin of 3-meth5ithiopropionaldehyde [3268-49-3]. 

Methionine sulfoxide [454-41-1, 62697-73-8] M 165.2, m >240 (dec). Likely impurities are dl-methionine sulfone and dZ-methionine. Crystd from water by adding EtOH in excess. 

The methionine nitrile (20 g) is dissolved in a solution prepared from 50 ml of aqueous 5N sodium hydroxide solution and 65 ml of ethanol. The solution is then refluxed for 24 hours ammonia is evolved. The solution is treated with activated carbon, filtered, acidified with glacial acetic acid (17 ml), chilled to -10°C and filtered to give crude product. This crude product is then slurried with a solution made up of 20 ml of water and 20 ml of methanol, filtered at -5° to -H0°C and dried to give dl-methionine as white platelets. 

Preparation by fermentation of Saccharomyces cerevisiae (baker yeast) with addition of L- or DL-methionine, lyse of cells with ethyl acetate and purification by ion-exchange chromatography. 

Breeding adults fed diets for 100 days containing 0, 1,2, 4, 8, or 16 mg Se/kg fresh weight (FW) ration as seleno-DL-methionine, or 16 mg Se/kg ration as seleno-DL-cysteine Breeding adults fed diets containing 0,... 

Day-old mallard ducklings fed diets for 2 weeks containing 0, 15, or 30 mg Se/kg ration in a 75% wheat diet (22% protein). Selenium given as seleno-DL-methionine, seleno-L-methionine, or selenized yeast... 

Adult males fed diets containing 0,10, 20, 40, or 80 mg Se/kg ration as seleno-DL-methionine for 16 weeks... 

Mallards fed diet containing 0 or 15 mg Se/kg ration as seleno-DL-methionine for 21 weeks, untreated food for 12 weeks, followed by 100 mg Se/kg ration for 5 weeks for both groups Adults fed diet containing 10 mg Se/kg ration as selenomethionine for 6 weeks followed by 6 weeks on untreated diet... 

Heinz, G.H., D.J. Hoffman, and L.J. LeCaptain. 1996. Toxicity of seleno-L-methionine, seleno-DL-methionine, high selenium wheat, and selenized yeast to mallard ducklings. Arch. Environ. Contamin. Toxicol. 30 93-99. 

Reaction of the binuclear complex [(bpy)Pd(p-OH)2Pd(bpy)]2+ with dl-methionine (met) obeys a simple second-order rate law (Aif = 46kJmol-1 AS = —101J K-1 mol-1). The mechanism suggested is rate-determining associative attack of the methionine-sulfur to give... 

D-Methionine, systematic name, formula, and molecular weight, 2 556t DL-Methionine... 

Freeman, H. C., and Golomb, M. L. (1970). Model compounds for metal-protein interaction Crystal structure of three platinum(Il) complexes of l- and DL-methionine and glycyl-L-methionine. Chem. Commun. pp. 1523-1524. 

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