Aspartic acid

Aspartic acid
IUPAC name Trivial: Aspartic acid Systematic: 2-Aminobutanedioic acid
Other names Aminosuccinic acid, asparagic acid, asparaginic acid[1]
Identifiers
CAS number	617-45-8 Y,  56-84-8 (L-isomer) 1783-96-6 (D-isomer)
PubChem	424
ChemSpider	411
EC-number	200-291-6
SMILES O=C(O)CC(N)C(=O)O
InChI InChI=1/C4H7NO4/c5-2(4(8)9)1-3(6)7/h2H,1,5H2,(H,6,7)(H,8,9) Key: CKLJMWTZIZZHCS-UHFFFAOYAE
Properties
Molecular formula	C4H7NO4
Molar mass	133.1 g mol−1
Hazards
EU Index	not listed
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Aspartic acid (abbreviated as Asp or D; Asx or B represent either aspartic acid or asparagine)^[2] is an α-amino acid with the chemical formula HO₂CCH(NH₂)CH₂CO₂H. The carboxylate anion of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins. Its codons are GAU and GAC.

Aspartic acid is, together with glutamic acid, classified as an acidic amino acid with a pKa of 4.0. Aspartate is pervasive in biosynthesis. As with all amino acids, the location of acid protons depends on the pH of the solution and the crystallization conditions.

Discovery

Aspartic acid was first discovered in 1827 by Plisson, synthesized by boiling asparagine (discovered in 1806) with a base.^[3]

Forms and nomenclature

The term "aspartic acid" refers to either of two forms or a mixture of two.^[2] Of these two forms, only one, "L-aspartic acid", is directly incorporated into amino acids. The biological roles of its counterpart, "D-aspartic acid" are more limited. Where enzymatic synthesis will produce one or the other, most chemical syntheses will produce both forms, "DL-aspartic acid".

Role in biosynthesis of amino acids

Aspartate is non-essential in mammals, being produced from oxaloacetate by transamination. In plants and microorganisms, aspartate is the precursor to several amino acids, including four that are essential: methionine, threonine, isoleucine, and lysine. The conversion of aspartate to these other amino acids begins with reduction of aspartate to its "semialdehyde," O₂CCH(NH₂)CH₂CHO.^[4] Asparagine is derived from aspartate via transamidation:

-O₂CCH(NH₂)CH₂CO₂- + GC(O)NH₃+ O₂CCH(NH₂)CH₂CONH₃+ + GC(O)O

(where GC(O)NH₂ and GC(O)OH are glutamine and glutamic acid, respectively)

Other biochemical roles

Aspartate is also a metabolite in the urea cycle and participates in gluconeogenesis. It carries reducing equivalents in the malate-aspartate shuttle, which utilizes the ready interconversion of aspartate and oxaloacetate, which is the oxidized (dehydrogenated) derivative of malic acid. Aspartate donates one nitrogen atom in the biosynthesis of inositol, the precursor to the purine bases.

Neurotransmitter

Aspartate (the conjugate base of aspartic acid) stimulates NMDA receptors, though not as strongly as the amino acid neurotransmitter glutamate does.^[5] It serves as an excitatory neurotransmitter in the brain and is an excitotoxin.

Sources

Dietary sources

Aspartic acid is not an essential amino acid, which means that it can be synthesized from central metabolic pathway intermediates in humans. Aspartic acid is found in:

• Animal sources: luncheon meats, sausage meat, wild game
• Vegetable sources: sprouting seeds, oat flakes, avocado, asparagus, young sugarcane, and molasses from sugar beets.^[1]
• Dietary supplements, either as aspartic acid itself or salts (such as magnesium aspartate)
• The sweetener aspartame (NutraSweet, Equal, Canderel, etc.)

Chemical synthesis

Racemic aspartic acid can be synthesized from diethyl sodium phthalimidomalonate, (C₆H₄(CO)₂NC(CO₂Et)₂).^[6]

References

See also

• Aspartate transaminase
• Sodium poly(aspartate), a synthetic polyamide
• American Chemical Society (21 April 2010). "Ancestral Eve' Crystal May Explain Origin of Life's Left-Handedness". ScienceDaily. http://www.sciencedaily.com/releases/2010/04/100421121501.htm. Retrieved 2010-04-21.