Aspartic acid

Aspartic acid
	; Skeletal formula of L-aspartic acid
Ball-and-stick model	Space-filling model
Names
	IUPAC name Trivial: Aspartic acid; Systematic: 2-Aminobutanedioic acid;
	Other names Aminosuccinic acid; Asparagic acid; Asparaginic acid;
Identifiers
CAS Number	L: 56-84-8 ; D/L: 617-45-8 ; D: 1783-96-6 ;
3D model (JSmol)	L: Interactive image; D: Interactive image; L Zwitterion: Interactive image; L Deprotonated zwitterion (aspartate): Interactive image;
ChEBI	L: CHEBI:17053 ; D/L: CHEBI:22660 ; D: CHEBI:17364 ;
ChEMBL	L: ChEMBL274323 ;
ChemSpider	L: 5745 ; D/L: 411 ; D: 75697 ;
DrugBank	L: DB00128 ;
ECHA InfoCard	100.000.265
EC Number	L: 200-291-6;
KEGG	D/L: C16433 ;
PubChem CID	L: 5960; D/L: 424; D: 83887;
UNII	L: 30KYC7MIAI ; D/L: 28XF4669EP ; D: 4SR0Q8YD1X ;
CompTox Dashboard (EPA)	L: DTXSID7022621 ;
	InChI InChI=1S/C4H7NO4/c5-2(4(8)9)1-3(6)7/h2H,1,5H2,(H,6,7)(H,8,9)/t2-/m0/s1 Key: CKLJMWTZIZZHCS-REOHCLBHSA-N ; D/L: Key: CKLJMWTZIZZHCS-UHFFFAOYSA-N; D: Key: CKLJMWTZIZZHCS-UWTATZPHSA-N;
	SMILES L: C([C@@H](C(=O)O)N)C(=O)O; D/L: C(C(C(=O)O)N)C(=O)O; D: C([C@H](C(=O)O)N)C(=O)O; L Zwitterion: C(C(C(=O)[O-])[NH3+])C(=O)O; L Deprotonated zwitterion (aspartate): C(C(C(=O)[O-])[NH3+])C(=O)[O-];
Properties
Chemical formula	C4H7NO4
Molar mass	133.103 g·mol−1
Appearance	colourless crystals
Density	1.7 g/cm3
Melting point	270 °C (518 °F; 543 K)
Boiling point	324 °C (615 °F; 597 K) (decomposes)
Solubility in water	4.5 g/L
Acidity (pKa)	1.99 (α-carboxyl; H2O); 3.90 (side chain; H2O); 9.90 (amino; H2O);
Conjugate base	Aspartate
Magnetic susceptibility (χ)	-64.2·10−6 cm3/mol
Hazards
NFPA 704 (fire diamond)	1 1 0
Supplementary data page
	Aspartic acid (data page)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. The L-isomer of aspartic acid is one of the 22 proteinogenic amino acids, i.e., the building blocks of proteins. D-aspartic acid is one of two D-amino acids commonly found in mammals. Apart from a few rare exceptions, D-aspartic acid is not used for protein synthesis but is incorporated into some peptides and plays a role as a neurotransmitter/neuromodulator.

Like all other amino acids, aspartic acid contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH⁺
₃ form under physiological conditions, while its α-carboxylic acid group is deprotonated −COO⁻ under physiological conditions. Aspartic acid has an acidic side chain (CH₂COOH) which reacts with other amino acids, enzymes and proteins in the body. Under physiological conditions (pH 7.4) in proteins the side chain usually occurs as the negatively charged aspartate form, −COO⁻. It is a non-essential amino acid in humans, meaning the body can synthesize it as needed. It is encoded by the codons GAU and GAC.

In proteins aspartate sidechains are often hydrogen bonded to form asx turns or asx motifs, which frequently occur at the N-termini of alpha helices.

Aspartic acid, like glutamic acid, is classified as an acidic amino acid, with a pK_a of 3.9; however, in a peptide this is highly dependent on the local environment, and could be as high as 14.

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