Amino acids aspartate

Fig. 2. Decomposition of aspartame to diketopipera2ine and/or aspartyl-phenylalanine and then to the amino acids aspartic acid and phenylalanine (22).

Some amino acids have side chains that bear- acidic or basic groups. As Table 27.3 indicates, these amino acids are characterized by three pK values. The third pK reflects the nature of the side chain. Acidic amino acids (aspartic and glutfflnic acid) have acidic side chains basic amino acids (lysine, arginine, and histidine) have basic side chains. 

Neotame is an artificial sweetener designed to overcome some of the problems with aspartame. The dimethylbutyl part of the molecule was added to block the action of peptidases, enzymes that break the peptide bond between the two amino acids aspartic acid and phenylalanine. This reduces the availability of phenylalanine, eliminating the need for a warning on labels directed at people who cannot properly metabolize phenylalanine. 

Ferritin is a globular iron-storage protein that stores iron as FeJ+. To leave the ferritin, Fe3+ must first be reduced to Fe2+. Ferritin has two types of channels through which the Fe"+ could leave a three-fold channel and a four-fold channel. The three-fold channel is lined with the amino acids aspartate (Asp) and glutamate (Glu) and the four-fold channel is lined with the amino acid leucine (Leu). Through which channel is the Fe + more likely to leave the ferritin protein Explain your answer. 

C HyNOi, a-Amino acid Aspartic acid W300... 

Next, add the four side chains in the positions marked R, R2, Rz, and Rj to give the final stmcture of the peptide. The leftmost amino acid, aspartic acid, is at the amino end. Aspartic acid is followed by methionine, valine, and tyrosine. Tyrosine is at the carboxyl end. Here are the individual amino acids, with their R groups highlighted ... 

Results from inhalation studies in animals suggest that hydrogen sulfide may be a developmental neurotoxicant. Neurochemical changes (in particular levels of the neurotransmitters gamma-aminobutyric acid, norepinephrine, and serotonin) and levels of the amino acids aspartate, glutamate, and taurine have been observed in various regions of the brain (Hannah et al. 1989, 1990 Skrajny et al. 

The relationship of the dicarboxylic amino acids, aspartic and glutamic acids to this process has also been studied (106). This investigation has been facilitated by a quantitative method for the codetermination (23) of the dehydrogenation indicator, resazurin, and its reduction product, resorufin. The wood destroying molds used were Trameles cinnabarina and Lentinus lepideus. 

The discovery of homochirality on a planet such as Mars could be an excellent biomarker and strengthen the argument for life on Mars. With an EE in the solar nebula there should be an EE on the surface of Mars of order 9 per cent but remains of ancient life on Mars would show a greater excess. The interchange of enantiomers occurs naturally in a process called racemisation and for the most labile amino acid, aspartic acid, the half-life for the racemisation is 800 years at 300 K in 800 years, half of the non-biotic aspartic acid would racemise and the EE would go to zero. In dry conditions, however, the half-life is much longer, perhaps as large as 5 x 104 years at 300 K. Extrapolation of the racemisation rate to 215 K, the equatorial temperature of Mars, extends the half-life further to 3 x 1012 years and to 1027 years at 150 K, Martian polar temperatures. Hence, discovery of a considerable EE in the Martian soil would be a strong indicator of ancient Martian life. 

Crystallographic studies have confirmed that a critical difference in the antiestrogenic action of raloxifene lies in the interaction of the alkylaminoethoxy side chain with the amino acid aspartate at position 351. The peculiar orientation of this side chain of the raloxifene molecule, an essential determinant of the antiestrogenic properties of the drug, is believed to account for its lack of endometrial activity (Clark et al. 1976 Grese et al. 1997 Bryant et al. 1998). 

Sowden et al. [4] also did detailed amino acid and amino sugar analyses of the soils from the different dimatic regions. The following amino acids were determined acidic amino acids aspartic and glutamic acids basic amino acids arginine, histidine, lysine and ornithine neutral amino adds, phenylalanine, tyrosine, glycine, alanine, valine, leudne, isoleudne, serine, threonine, proline and hydroxyproline ... 

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. 

The amino acids, aspartate and glutamate, are not taken up from the blood but are synthesised in the brain. This requires nitrogen (for the -NH2 groups) which is obtained from branched-chain amino acids via transamination, as in other tissues. 

The amino acids in question are the basic amino acids lysine, arginine, and histidine, and the acidic amino acids aspartic acid and glutamic acid. The side-chain functions of these amino acids, ionized at pH 7 (see Box 4.7), act as acids or bases. In a reverse sequence, protons may be acquired or donated to regenerate the conjugate acids and conjugate bases. 

The amino group of cysteamine is bound to the carboxy group of another biogenic amine via an acid amide bond (-CO-NH-). [1-Alanine arises through decarboxylation of the amino acid aspartate, but it can also be formed by breakdown of pyrimidine bases (see p. 186). 

The acidic amino acids, aspartic acid and glutamic acid, have carboxyl groups. 

Malate is oxidized to oxaloacetate by malate dehydrogenase (Figure 9.7). This reaction produces the third and final NADH of the cycle. [Note Oxaloacetate is also produced by the transamination of the amino acid, aspartic acid.]... 

The atoms of the purine ring are contributed by a number of compounds, including amino acids (aspartic acid, glycine, and glutamine), CO2, and N10-formyltetrahydrofolate (Figure 22.5). The purine ring is constructed by a series of reactions that add the donated carbons and nitrogens to a preformed ribose 5-phosphate. (See p. 145 for a discussion of ribose 5-phosphate synthesis by the HMP pathway.)... 

The atoms of a purine are contributed by amino acids (aspartic acid, glutamine, and glycine), CO2, and N10-formyl tetrahydrofolic acid. 

It may be seen from Table II that there is good agreement in general between the reports from the various laboratories. It is worth noting, as Arens et al. (65) have done, that about 50% of the molecule is composed of only five amino acids aspartic acid, threonine, alanine, valine, and glycine. Whether the differences that are reported result from experimental variation in the analyses, real differences between strains, or different proportions of isoenzymes in the enzymes examined remains to be seen. As mentioned in another section, the Bayer group (65) found... 

An additional point should be noted from table 3.3. Whereas the amino acid side chains (R groups) that are normally charged at physiological pH are restricted to five amino acids (aspartic acid, glutamic acid, lysine, arginine, and sometimes histidine), a number of potentially ionizable R groups are part of other amino acids. These include cysteine, serine, threonine, and tyrosine. The ionization reac-... 

FIGURE 11 The effects of phosphate buffer concentration (ionic strength) on the chiral resolution of (a) rf-ephedrine ( ), /-ephedrine ( ), (/-norephedrine ( ), and /-norephedrine (O) and (b) the dansyl amino acids aspartic acid (A), glutamic acid (O), serine ( ), and phenylalanine (V) on /1-CD columns. (From Refs. 65,70.)... 

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