Aspartic Acid

  Aspartic acid is a non-essential and acidic amino acid.  Aspartic acid is abbreviated as Asp or D.  Aspartic acid was first recognized in 1868 when it was first isolated from legumin in plant seeds.  Aspartic acid is a non-essential amino acid for mammals which means that enough aspartic acid is synthesized by the body from oxaloacetic acid which is formed in metabolism of carbohydrates.  Aspartic acid is found in many different sources of food such as dairy, beef, poultry and sprouting seeds.  Here is a high quality representation of the structure of aspartic acid:

  Aspartic acid's molecular formula is C₄H₇NO₄ and has a molecular weight of 133.10 grams/mole. Aspartic acid is the one of only two amino acids that give a negatively charged carboxylic group on the side chain.  The functional groups present within aspartic acid are an amine and two carboxylic groups.  Aspartic acids are play a vital role as acids in enzyme active centers and also function in maintaining the solubility and ionic character of proteins.  This amino acid is one of the only two acidic amino acids.  There are three pKa values for aspartic acid which are: 1) alpha-carboxylic - 2.10;   2) alpha-amino -  9.82;  3) side chain  -  3.86.  The side chain is a carboxyl group located on the amino acid.  The isoelectric point for aspartic acid is 2.77 pH. 
 
Sources:
1.  Mayer, Michael. "Aspartic acid information page. All about aspartic acid and the role it plays in your diet." Zest for Life vitamins and supplements. 24 Jan. 2011. 24 Mar. 2011 http://www.anyvitamins.com/aspartic-acid-info.html.

2.  Kirste, Burkhard. "Aspartic Acid." Institut für Chemie und Biochemie an der FU Berlin. 23 Jan. 1998. 24 Mar. 2011 http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/asp_en.html.

3.  "Amino Acids - Aspartic Acid." The Biology Project. 24 Sept. 2003. 24 Mar. 2011 http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aspartate.html.

4.  Parrill, Abby. "Amino Acid Structures." Michigan State University. 4 Feb. 1997. Department of Chemistry. 24 Mar. 2011 http://www.cem.msu.edu/~cem252/sp97/ch24/ch24aa.html.