Key Sources and Roles of Aspartic Acid in Biological Systems
Aspartic acid is an acidic amino acid with functional groups of two carboxylic groups along with one amino group. There are about 20 important types of amino acids that are found in nature, more on this later. Every amino acid molecule is made up of two functional groups, they are opposite in characteristics, one is an amino group, and then there is a carboxylic acid. An aspartic acid structure is no exception; it contains one α-amino group which is in NH3+ forms and the carboxylic group that is in deprotonated –COO-. The aspartic acid formula looks like this- (C4H7NO4). Aspartic acid is a non-essential amino acid as the human body can synthesize it as it is needed. Aspartic acid can be found in a plethora of eatables including oysters, avocado, sugar beets etc.
Why Is Aspartic Acid Different From Other Amino Acids?
As we previously discussed that amino acid has two functional groups, here we will dive a little deeper and shine some light on the third group, the R-group or the side chains, that gives the aspartic acid structure a distinction from the other amino acids such as glycine or cysteine. The R-group of the amino acids exerts profound changes in the biological activity of proteins. Amino acids are generally classified based on the characteristics of the functional group on the side chain in a neutral pH medium. They can be polar or nonpolar, polar yet charged, negatively charged or positively charged. The carboxyl group that is present in the side chain of the aspartic acid structure is ionized at physiological pH, which is known as aspartate, it is also from where the acid gets its name from. Glutamic acid also shares this sub-category with aspartic acid, the ionized carboxyl group in Glutamic Acid is known as glutamate.
Aspartic acid is a non-essential amino acid; it plays a vital part in the synthesis of amino acids and the citric acid and urea cycles. Aspartic acid commonly occurs in its L-form. It is found in plants and animals, especially in sugar beets and sugar cane. Here is a quick table consisting of the sources of this acid
Sources Of Aspartic Acid
Aspartic Acid Structure And Types Of Aspartic Acid
Aspartic acid is a dicarboxylic amino acid that means it is an acidic polar α-amino acid with two carboxylic groups and one of the carboxyl groups is attached with one additional methylene group. Aspartic acid has the isoelectric point of 2.77, because of these two carboxylic groups. It is also called ‘succinic acid’. The presence of the second carboxyl group makes it very hydrophilic, it has pKA of 3.85, and this group can also form an ionic bond with almost any metallic ion and also participate in a dipole interaction with water. As an aspartic acid molecule is negatively charged in neutral pH, it can be found at the surface of proteins. The carboxyl group bonded on alpha-carbon has a pKa value of 1.88; -COOH group at the side chain has the value of 3.65 and 9.60 for the amino group. The aspartic acid formula is C4H7NO4, and the aspartic acid structure looks like this –
There are two enantiomers of the aspartic Acid, namely- L-aspartic Acid, D-aspartic Acid. There is not much difference between these two. The first one is directly incorporated into proteins, but D-aspartic acids are more limited. Enzymatic synthesis can produce either of these acids.
Aspartic Acid Hybridization
The molecular aspartic acid formula is HOOCCH(NH2)CH2COOH and has the molecular weight of 133.1g/mol.
Aspartic acid has the IUPAC name- 2-Aminobutanoic acid.
The atoms that are inside part of the aspartic acid have sp2 hybridization.
The nitrogen atom is touching three other atoms, i.e. one carbon and two hydrogen atoms. It is sp3 hybridized.
C1 and C4 are sp2 hybridized with trigonal planar geometry with 120o angle. The other two carbon atoms, i.e. C2 and C3, are sp3 hybridized with tetrahedral geometry in a 109o bond angle.
The carbon atoms in the carboxyl groups are sp2 hybridized.
Examples
What Type of Acid is Aspartic Acid?
Answer: Aspartic acid is a non-essential acidic amino acid.
What is The Aspartic Acid Formula and Its Molecular Weight?
Answer: The chemical formula of aspartic acid is C4H7NO4 and its molecular weight is 133.1g/mol.
What Are The Two Functional Components of Aspartic Acid?
Answer: The two functional components of aspartic acid are one amino group and two carboxyl groups.
What Are The Two Types of Aspartic Acid?
Answer: There are two types of aspartic acid i.e. L-aspartic acid and D-aspartic acid.
Did You Know
The aspartic Amino acid is a non-essential amino acid; in mammals, the synthesis of this amino acid is self-regulatory through the central metabolism pathway. You won’t be out of breath after running four yards if you eat oysters and avocados more since it has a significant level of aspartic amino acid. Amino acids are the building blocks for the proteins in your body.
FAQs on Aspartic Acid: Structure, Functions, and Significance
1. What are the key functions of aspartic acid in the body?
Aspartic acid, a non-essential amino acid, performs several vital roles. Its primary function is as a building block for proteins. It also acts as a precursor for other essential amino acids like methionine and lysine. Additionally, it participates in the urea cycle to help remove excess ammonia from the body and functions as an excitatory neurotransmitter in the central nervous system, particularly in its aspartate form.
2. Which functional groups define the structure of aspartic acid?
The structure of aspartic acid (C₄H₇NO₄) is defined by three key functional groups attached to a central alpha-carbon atom:
- An amino group (-NH₂)
- A primary carboxyl group (-COOH)
- A side chain containing a second carboxyl group (-CH₂COOH)
3. Why is aspartic acid classified as an acidic amino acid?
Aspartic acid is classified as an acidic amino acid because its side chain contains a second carboxyl group (-COOH). At physiological pH (around 7.4), both of its carboxyl groups tend to lose a proton (H⁺) and become negatively charged carboxylate ions (-COO⁻). The presence of this extra acidic functional group gives the molecule an overall net negative charge and its distinct acidic character, distinguishing it from neutral or basic amino acids.
4. What is the main difference between aspartic acid and its conjugate base, aspartate?
The primary difference is their state of protonation. Aspartic acid refers to the molecule in its fully protonated form, with its carboxyl groups as -COOH. Aspartate is the deprotonated, or conjugate base, form. In the body's physiological pH, aspartic acid typically exists as aspartate, where the carboxyl groups have lost a proton to become negatively charged -COO⁻ ions. Aspartate is the biologically active form involved in most metabolic pathways and neurotransmission.
5. What are some common natural sources of aspartic acid?
While the human body can synthesise aspartic acid, it is also abundant in many protein-rich foods. Key sources include:
- Animal-based sources: Poultry (chicken, turkey), beef, eggs, and dairy products like milk and cheese.
- Plant-based sources: Asparagus, soy products, peanuts, sprouting seeds, oats, and avocados.
6. How does L-aspartic acid differ from D-aspartic acid in terms of biological significance?
L-aspartic acid and D-aspartic acid are stereoisomers (enantiomers), meaning they are non-superimposable mirror images of each other. Their biological roles are completely different:
- L-aspartic acid is the isomer used by the body for protein synthesis and is incorporated into polypeptide chains.
- D-aspartic acid is not used to build proteins but serves specialised functions, primarily in the nervous and endocrine systems, where it acts as a neurotransmitter and regulates hormone synthesis.
7. How does aspartic acid's structure compare to glutamic acid?
Aspartic acid and glutamic acid are both classified as acidic amino acids due to a second carboxyl group in their side chains. The only structural difference between them is the length of the side chain. Aspartic acid's side chain has one methylene group (-CH₂COOH), while glutamic acid's side chain is one carbon longer, containing two methylene groups (-CH₂CH₂COOH). This small difference in size impacts how they fit into protein structures and enzyme active sites.
