What is the difference between aspartate and aspartic acid

Also shown are the interatomic distances of the proximate oxygen residues energy minimized and the molecular surface area. For glutamate, these are 4. Not only does glutamic acid induce helicity to a greater extent than its homologs Kohn et al. Examples of such polyglutamate-rich sequences occur in nucleoplasmic protein where they are required for facilitated translocation of the protein through the nuclear pore complex Vancurova et al.

Further, with respect to glutamate sequences, the microtubule cytoskeleton of eukaryotic cells is involved in many essential cellular functions. Here, the post-translational modification of tubulin by polyglutamylation MacRae regulates its interaction with microtube-associated proteins Bolinnec et al. Thus, glutamate may be seen here to play a role in the formation and function of the cystoskeleton Audebert et al. Finally, the importance of folylpolyglutamates might be noted, in which these derivatives are intracellular substrates and regulators of one-carbon metabolism and their synthesis is required for normal folate retention by cells Shane Another difference between glutamate and aspartate is that although both are acidic residues, and have similarly low p K a and isoelectric points, the extra methylene group of glutamate invests it with a greater dipolar moment and therefore a dramatically different hydrophobic effect.

Compared with glycine, whose hydrophobic effect is 1. When deprotonated, glutamate becomes highly hydrophilic by a fivefold greater factor than aspartate; thus its amphiphilic nature invests glutamic acid with a unique position among the polar amino acids as determined both by physicochemical studies Karplus and by the effect of residue substitutions in site-directed mutagenic experiments on protein structure Bordo and Argos The significance of glutamate in nature, particularly in mammalian metabolism relative to its homologs, might also be appreciated by considering the reactivity of the molecule Fig.

A presentation of some of the intramolecular, reactive features of glutamate that account for its determinant role in metabolism and possibly its abundance in nature. All three of the dicarboxylic amino acids form imines Schiff bases with pyridoxal phosphate PLP , the ligand responsible for transamination. But the range of tautomers available to serve as activated or transient states is severely restricted in the case of aspartate, especially because enolization toward the 2,3-configurations is unfavored by the electron-withdrawing nature of its 4-keto carboxylic group.

The 4-methylene group in glutamate and of amino adipic acid stabilizes this tautomer and its transient ketimine-stabilized carbanion; as a consequence, the Schiff base half-life for glutamate vs. Thus, glutamate will release its nitrogen to transaminating amino acids, whereas aspartate exchanges its N only with glutamate Novogrodsky and Meister , an observation that has been confirmed extensively from both a theoretical and a practical point of view on the mechanism of PLP-mediated enzyme action Meister But the essential determinant for the course of these catalyzed reactions is the specific stereoconfiguration of glutamate, alluded to earlier, with respect to the position of its two carboxyls and relative to the amine-imine functionality.

Aspartic acid is not a substrate for this dehydrogenase system and 2-aminoadipic acid shows only 0. The significance of this metabolic reaction is well illustrated by the recent identification of a new form of congenital hyperinsulinemia and hyperammonemia syndrome due to mutations in the glutamate dehydrogenase gene that impair the control of the activity of the enzyme Stanley et al. Finally, a similar argument about stabilization of resonant activated intermediates applies to the action of glutamate decarboxylase O'Leary and Koontz , which supplies 4-aminobutyric acid.

The latter is not only a neurotransmitter, but the reaction affords a mechanism for the recycling of the glutamate carbon skeleton into succinate. Aspartic acid and 2-aminoadipic acid are not substrates in this type of transformation, possibly because of their inability to sustain the requisite activated states O'Leary et al.

These are the activated intermediate states that permit trapping of CO 2 in the formation of carboxyglutamate acid Vermeer , homolytic rearrangement to 3-methyl-aspartate under the action of B—dependent enzymes Marsh and Ballou and alkylation, as an entry point for biosynthesis and natural products.

This property accounts for the numerous vitamin K—dependent proteins, which contain post-translationally carboxylated glutamic residues that are involved in blood coagulation, the proteins in calcified tissues such as osteocalcin a negative regulator of bone formation and matrix Gla protein a calcification inhibitor , as well as a number of others such as nephrocalcin and plaque Gla proteins, whose functions remain unclear Ferland This domain has a high affinity for calcium.

Enolization at the 4,5-position, including resonance tautomer stabilization by the electronic properties of the 3-methylene, undoubtedly endows glutamate with the unique ability to sustain redox reactions at the 5-carboxyl, affording the transient glutamic semialdehyde species, which is the precursor for proline and ornithine synthesis and the intermediate for the reverse flux of these latter amino acids into glutamate as part of the metabolic elaboration of the arginine cycle Jones , Wakabayashi Aspartate cannot sustain redox at the 4-carboxyl, which would not be resonance stabilized, just as its 2-position is not stabilized in the contexts already described.

The reactivity at the 5-carbon of glutamate is also characterized by the well-known fact that this position readily forms amides. Glutamate and aspartate each yield glutamine and asparagine, respectively. Further, it is really not possible to consider glutamate metabolism in the mammalian organism in any comprehensive way without bringing glutamine into the picture.

This would introduce a large area of contemporary amino acid metabolic research, but this is beyond the remit of this presentation. A number of reviews on glutamine function and metabolism might be consulted for further details Curthoys and Watford , Newsholme and Calder , Souba , and Also, it has been proposed recently that glutamate serves as a vehicle for the transport of nitrogen, arising from the catabolism of N-rich amino acids, out of the central nervous system Lee et al.

Additionally, the spectrum of terminal amidations is greatly augmented, in the case of glutamate, by its ability to form a thermodynamically stabilized, five-member lactam, 5-oxoproline. Aspartate cannot form a lactam, which would be a very unfavorable four-member and strained ring structure. The six-member lactam ring of 2-aminoadipic acid, in contrast, is a thermodynamically stable end product. These make it a favorable choice, if not the only one, for facilitating metabolic processes that play major roles in the nitrogen economy of the host and in reference to structure-function relationships of a variety of key cellular proteins.

Above we have attempted to consider the question: why the generous abundance of glutamate in Nature? We are left, therefore, with the task of making a few comments about advances in our understanding of the physiology of glutamate metabolism since Munro reviewed this topic two decades ago.

These represent two areas of investigation in which significant advances have been made since the First International Glutamate Symposium Filer et al. Further and more elaborate presentations of advances are given elsewhere in these proceedings. Blood concentrations of glutamine are very much higher than for glutamate Table 2 Forslund et al.

Plasma glutamate, glutamine, phenylalanine and aspartate concentrations at different protein intakes: postabsorptive 1. Comparison of the concentrations of various amino acids in the free pools of muscle 1. In comparison to leucine and threonine, for example, in which a protein-rich meal causes parallel increases in concentrations in plasma and muscle, there are no significant or major changes in either plasma or muscle glutamate and glutamine levels Fig.

In contrast, the concentrations of plasma glutamate and glutamine in blood drawn from subjects in the postabsorptive state appear to be affected by the chronic level of dietary protein intake, especially when comparing concentration changes within the supramaintenance range of intake Table 2.

In our recent studies, conducted in collaboration with the Uppsala group Forslund et al. The metabolic basis for and functional significance of this response in circulating glutamine and glutamate levels to a high protein intake is not clear. Changes in plasma and free amino acid concentrations of skeletal muscle 1 h after a high protein meal in healthy adults. Note the lack of significant change in glutamate or glutamine. Slightly modified from Bergstrom et al. Plasma glutamine concentrations throughout a continuous h period for groups of young adult men receiving either normal 1 g or high 2.

Since that time, direct estimates have been made of glutamate and glutamine flux, using tracer techniques. An example of these is also given in Table 4. The following two points might be made: 1 it seems that the tracer-derived values underestimate the flux of glutamate and glutamine due to protein turnover.

This is probably due to the fact that measurement of the plasma glutamate and glutamine isotopic abundances overestimates those in the extravascular pools and thus the flux will be underestimated. On the other hand, Van Acker et al. Body flux of glutamate, glutamine and leucine in adult men: postabsorptive state 1. From Matthews and Campbell based on 20350glutamate and [2-N]glutamine as tracers, respectively. From Blomstrand et al. It seems relevant, in relation to the effect of chronic protein intake on plasma levels as noted above, that the rates of de novo synthesis of glutamate and glutamine change with the dietary protein level.

As summarized in Table 5 , Matthews and Campbell reported a significant decline in both glutamate and glutamine de novo synthesis rates when dietary protein intake was increased from a level sufficient to meet requirements [0.

However, the site s at which this response occurs possibly muscle; Nurjhan et al. Estimates of the rates of glutamate and glutamine synthesis at different protein intakes 1.

From Matthews and Campbell On the basis of the work of Windmueller , Windmueller Spaeth and and Neame and Wiseman , it was clear to Munro in that the intestinal tissues were responsible for a significant metabolism of dietary glutamate and glutamine. Since then, elegant stable isotope studies have extended our understanding of the quantitative handling by the intestine of dietary glutamate and glutamine, with a confirmation that little or no dietary glutamate enters either the systemic Matthews et al.

Additionally, a significant fate of glutamate is glutathione synthesis Reeds et al. These findings are discussed in detail elsewhere in these proceedings but they are highlighted here as exciting examples of our understanding about the quantitative aspects of the physiology of glutamate metabolism. A net effect of the extensive intestinal metabolism of glutamate is the achievement of relatively stable plasma concentrations of glutamate and glutamine throughout the fasting and fed periods of the h day Fig.

The origin and reactivity of glutamate have been reviewed, somewhat selectively, with the purpose of developing an initial understanding of the considerable abundance of L-glutamate in Nature and its dominant role in the nitrogen and energy economies of the mammalian organism.

We propose that insight can be forthcoming by considering the reactivity of the molecule itself. In addition, we have touched upon recent advances in the study of glutamate metabolism, at the whole-body level, with a further clarification of the fact that glutamate metabolism in vivo is highly compartmented.

This endows it with the opportunity to participate effectively in a number of distinct and possibly competitive roles, including that of a nutrient, energy-yielding substrate, structural determinant, enzyme regulator and excitatory molecule.

However, because of their breadth it may be that we have not entirely succeeded in addressing the issues posed to us at the outset.

Audebert , S. Cell Sci. Google Scholar. Bailey , J. Circular polarization in star-formation regions: implications for biomolecular homochirality Science Washington DC — Battezzati , A. Beutler , E. Bergstrom , J. Blomstrand , E. What is Aspartate — Definition, Charge, Role 2. It is the most common form of the amino acid that occurs under physiological conditions of the body. It plays a key role in urea cycle by donating amino groups to the formation of urea.

It also participates in the malate-aspartate shuttle of the gluconeogenesis. In addition, it is the amino acid which provides a nitrogen atom for the synthesis of inosine. Moreover, it serves as an excitatory neurotransmitter like glutamate but, its effect is as not strong as glutamate.

Aspartate serves as a precursor for the synthesis of several amino acids including methionine, threonine, lysine, and isoleucine in plants and microorganisms. Try again? Cited by. Download options Please wait Supplementary information PDF K.

Article type Paper. Submitted 14 Jul Accepted 02 Oct First published 11 Oct Download Citation. Green Chem. Request permissions. Unusual differences in the reactivity of glutamic and aspartic acid in oxidative decarboxylation reactions A. You are using an unsupported browser.

Please upgrade your browser to a newer version to get the best experience on Human Metabolome Database. MrvD 9 8 0 0 1 0 V 5. Download Close. Show all enzymes and transporters. Enzyme Details. General function: Involved in transferase activity, transferring nitrogenous groups Specific function: Plays a key role in amino acid metabolism By similarity. J Biol Chem. Epub Jun 1. Acta Chir Belg. J Neurochem. Epub Apr Basic Clin Pharmacol Toxicol. Clin Biochem. Epub Jan General function: Involved in transferase activity, transferring nitrogenous groups Specific function: Catalyzes the irreversible transamination of the L-tryptophan metabolite L-kynurenine to form kynurenic acid KA.

Plays a key role in amino acid metabolism. Important for metabolite exchange between mitochondria and cytosol. Facilitates cellular uptake of long-chain free fatty acids. Nat Rev Drug Discov. J Bacteriol. Ciba Found Symp. Nucleic Acids Res. General function: Involved in nucleic acid binding Specific function: Endonuclease that catalyzes the cleavage of RNA on the 3' side of pyrimidine nucleotides.

General function: Involved in metallopeptidase activity Specific function: Involved in the hydrolysis of N-acylated or N-acetylated amino acids except L-aspartate. J Biochem. General function: Involved in hydrolase activity, acting on ester bonds Specific function: Catalyzes the deacetylation of N-acetylaspartic acid NAA to produce acetate and L-aspartate. NAA occurs in high concentration in brain and its hydrolysis NAA plays a significant part in the maintenance of intact white matter.

In other tissues it act as a scavenger of NAA from body fluids. Epub Dec Childs Nerv Syst. Prog Neurobiol. Epub Jan 5. General function: Involved in hydrolase activity, acting on ester bonds Specific function: Plays an important role in deacetylating mercapturic acids in kidney proximal tubules By similarity.

EMBO J. Epub Apr 5. Nitric Oxide. Epub Aug 3. Clin Chim Acta.