Aspartic acid isolation

A change in the concentration of labelled aspartic acid in the general metabolic pool leads to a corresponding change in the specific activity of aspartic acid isolated from different peptide fragments of the mycobacillin molecule, suggesting that mycobacillin synthesis occurs by the way of linear addition of amino acids to the peptide chain (Banerjee and Bose, 1964 a). 

Fumaric acid occurs naturally in many plants and is named after Fumaria officinalis, a climbing aimual plant, from which it was first isolated. It is also known as (E)-2-butenedioic acid, aHomaleic acid, boletic acid, Hchenic acid, or /n j -l,2-ethylenedicarboxylic acid. It is used as a food acidulant and as a raw material in the manufacture of unsaturated polyester resins, quick-setting inks, furniture lacquers, paper sizing chemicals, and aspartic acid [56-84-8]. 

A solution of 88.5 parts of L-phenylalanine methyl ester hydrochloride in 100 parts of water is neutralized by the addition of dilute aqueous potassium bicarbonate, then is extracted with approximately 900 parts of ethyl acetate. The resulting organic solution is washed with water and dried over anhydrous magnesium sulfate. To that solution is then added 200 parts of N-benzyloxycarbonyl-L-aspartic acid-a-p-nitrophenyl, -benzyl diester, and that reaction mixture is kept at room temperature for about 24 hours, then at approximately 65°C for about 24 hours. The reaction mixture is cooled to room temperature, diluted with approximately 390 parts of cyclohexane, then cooled to approximately -18°C in order to complete crystallization. The resulting crystalline product is isolated by filtration and dried to afford -benzyl N-benzyloxycarbonvI-L-aspartyl-L-phenylalanine methyl ester, melting at about 118.5°-119.5°C. 

In the published synthesis the ozonolysis is performed on the protected product (9) and aldehyde (10) isolated before oxidation, hydrolysis and decarboxylation give aspartic acid. 

Aminopeptidase A is another brush border membrane enzyme which has been the subject of various studies [79,81,83-86], It has been found in the intestinal brush border membrane of humans, rabbits, rats, and pigs and is active against peptides with acidic amino acids at the amino terminus. Its activity against dipeptides is more limited. Shoaf et al., isolated three rat brush border aminopeptidases with distinct but somewhat overlapping substrate specificities. These enzymes had preference for dipeptides containing methionine, arginine, or aspartic acid and glycine. The optimal pH for activity of aminopeptidase was reported to be 7-8. 

As early as 1905 Abderhalden (Al) isolated from the hydrolyzate of the nondiffusible fraction of human urine four amino acids, i.e., leucine, alanine, glycine, and glutamic acid, and detected two others phenylalanine and aspartic acid. Some amino acids derived from this fraction have been quantitatively determined by Albanese et al. (A3) who found in the amount of the nondiffusible fraction corresponding to one liter of urine as much as 32.8 mg tryptophan, 18.0 mg phenylalanine, 16.2 mg methionine, 15.2 mg cystine, 13.1 mg arginine, 6.7 mg histidine, and 3.9 mg tyrosine. 

In the course of studies on aminoaciduria in Fanconi s syndrome, Dent (Dl) isolated from the urine of the subject investigated a simple peptide identified as serylglycylglycine. Carsten (Cl) found in normal urine several peptides containing in every case one of the dicarboxylic amino acids. He discovered also two tetrapeptides, one of them consisting of equimolar amounts of aspartic acid and glycine, and the second composed of glycine, alanine, and glutamic acid in the ratio 2 1 1. The first of these tetrapeptides was also found in the urine of a patient with rheumatoid arthritis. 

By means of a procedure described above, Hanson and Fittkau (HI) isolated seventeen different peptides from normal urine. One of them, not belonging to the main peptide fraction, consisted of glutamic acid, and phenylalanine with alanine as the third not definitely established component. The remaining peptides contained five to ten different amino acid residues and some unidentified ninhydrin-positive constituents. Four amino acids, i.e., glutamic acid, aspartic acid, glycine, and alanine, were found in the majority of the peptides analyzed. Twelve peptides contained lysine and eight valine. Less frequently encountered were serine, threonine, tyrosine, leucine, phenylalanine, proline, hydroxyproline, and a-aminobutyric acid (found only in two cases). The amino acid composi-... 

There is only a small selection of nonprotein amino acids that contain carbonyl groups in the form of ketone, aldehyde, and carboxylic acid moieties, as part of the side chain. The examples given in Table 6 are components of nonribosomal peptides isolated from bacteria or fungi and siderophores from bacteria. The biosynthesis of these amino acids is not clear however, some of the amino acids with carboxylic acid side chains may be traced back to the L-a-amino acids aspartic acid and glutamic acid. 

Biological. Incubation of C-ring labeled endothall (10 mg/mL) by Arthwbactersp., which was isolated from pond water and a hydrosol, in aerobic sediment-water suspensions revealed that after 30 d, 40% evolved as CO2. Glutamic acid was the major transformation product. Minor products were alanine, citric, and aspartic acids and unidentified products, some of which were tentativeiy identified as phosphate esters (Sikka and Saxena, 1973). In pond water treated with endothall (2 and 4 ppm), detectable levels were found after 7 d (Sikka and Rice, 1973). Biodegradation was rapid in an Ontario soil sample. After 1 wk, 70% of endothall added was converted to carbon dioxide (Simsiman et al, 1976). 

Isopyoverdins contain the siderophore Fig. 1, Chrb with aspartic acid as the first amino acid. They have been encountered so far only in isolates from Pseudomonas putida strains, e.g. BTPl 168) 6). 

Peptide toxins. Of all the toxins produced by freshwater cyanobacteria, the peptide toxins of Microcystis aeruginosa have received the most attention. All research on these peptide toxins indicates they are small, possibly cyclic, with molecular weights estimated at 1200 to 2600 (10,11). Recent work has become more definitive in the estimation of molecular weight and amino acid composition. In 1978 Elleman et al. (12) reported that they had isolated and characterized the peptide toxin of an Australian strain Microcystis which was a pentapeptide with a minimum molecular weight of 654. It consisted of equimolar amounts of alanine, tyrosine, methionine, glutamic and 3-methyl aspartic acid and methylamine. 

Glutamic Acid.—The greater part of the glutamic acid is isolated as hydrochloride before the mixture of amino acids is esterified. It is contained with aspartic acid ester in the aqueous solution after the phenylalanine ester has been extracted by ether, and it is separated from aspartic acid, after hydrolysis by baryta, by conversion into its hydrochloride from this it is obtained by treatment with the calculated quantity of soda to combine with the hydrochloric acid and by crystallisation from water, in which it is soluble with some difficulty. 

Aspartic Acid.—A portion of the aspartic acid, after separation from phenylalanine ester and after hydrolysis by baryta, may separate as barium salt this is the barium salt of racemic aspartic acid. The remainder is isolated, when the glutamic acid has been removed as hydrochloride, by boiling with lead hydroxide and treating with hydrogen sulphide to remove hydrochloric acid and lead respectively, and by crystallising from water. It maybe characterised by conversion into its copper salt, or by analysis, and is estimated by its weight. 

Asparagine, the amide of aspartic acid, was first isolated by Robi-quet and Vauquelin, in 1806, from the juice of Asparagus officinalis hence its name. Not only is asparagine found in asparagus, but also in the seedlings of lupines, peas, vetches, etc., from which it is best and most easily prepared. 

The role of aspartic acid and glutamic acid was investigated in BMP (Beefy Meaty peptide, Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala) isolated from enzymatic digests of beef soup. The taste of BMP was affected by the sequence of acidic fragment. Sodium ion uptake of acidic dipeptides and their taste, when mixed with sodium ion, were dependent on the component and/or sequence of dipeptides containing acicHc amino acids. 

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