L-ASPARTIC ACID

L‑Aspartic acid (L‑Asp) is a naturally occurring, non-essential α‑amino acid with the molecular formula C₄H₇NO₄. 
It plays pivotal roles in protein biosynthesis, nitrogen metabolism, neurotransmission, and as a precursor in various biosynthetic pathways. 
This article reviews its chemical and physical properties, nomenclature, biosynthesis, metabolism, biological functions, industrial and medical applications, analytical methods for detection and quantification, safety and toxicological profiles, and the distinctions and significance of its stereoisomers. 
Future research directions and unresolved scientific questions are highlighted.

Introduction
Definition and Chemical Structure
L‑Aspartic acid is an α‑amino acid characterized by the presence of two carboxyl groups (making it an acidic amino acid) and an amino group attached to the α‑carbon. 
The chemical formula is C₄H₇NO₄ with a molecular weight of 133.10 g/mol. 
The molecule contains one chiral center at the α‑carbon, resulting in L (S) and D (R) stereoisomers, with the L‑form being the biologically active variant incorporated into proteins.

Historical Context
L‑Aspartic acid was first isolated in 1827 by Auguste-Arthur Plisson and Étienne Ossian Henry from asparagine hydrolysis. 
Since then, it has been studied extensively due to its biological importance and industrial applications.

Biological Significance
L‑Aspartic acid is a key participant in metabolic pathways including the tricarboxylic acid (TCA) cycle and the urea cycle. 
It also functions as a neurotransmitter and participates in biosynthetic processes, including the synthesis of other amino acids and nucleotides.

CAS Registry Number and Synonyms
CAS Number (L‑Aspartic acid): 56‑84‑8
Synonyms: L‑2‑Aminobutanedioic acid, Aminosuccinic acid, (S)‑Aminosuccinic acid, L‑Asp, Asparagic acid, L‑(+)-Aspartic acid, L‑α‑Aminosuccinic acid

Chemical & Physical Properties
Molecular Properties
Formula: C₄H₇NO₄
Molecular Weight: 133.10 g/mol
Density: 1.66 g/cm³
Appearance: White crystalline powder
Melting Point: > 300 °C (decomposes)

Acid-Base Behavior and pKa Values
L‑Aspartic acid exhibits acidic properties due to its two carboxyl groups. The pKa values for L‑Aspartic acid at 25 °C are approximately:
α‑carboxyl group: 1.99
β‑carboxyl group (side chain): 3.90
α‑amino group: 9.90
These pKa values result in distinct ionization states depending on pH, with the zwitterionic form predominating near physiological pH (~7.4).
Solubility
Water solubility: ~5 g/L at 25 °C (increases with temperature)
Insoluble in organic solvents such as ether and chloroform
Slightly soluble in alcohols

Optical Properties
Optical Rotation: +32° (c = 1, 6N HCl) for L‑Aspartic acid
Important for confirming enantiomeric purity

Nomenclature & Registry
IUPAC Nomenclature
(2S)‑2‑Aminobutanedioic acid
Systematic name reflects stereochemistry and functional groups.

Registry Numbers & Database Identifiers
CAS: 56‑84‑8 (L‑Aspartic acid)
PubChem CID: 5960
CHEBI: 17053
DrugBank: DB00128
KEGG: C0004
HMDB: HMDB0000194
Cross-referencing these ensures accurate chemical identification in various scientific contexts.

Synonyms in Detail
Synonym    Source / Context
L‑2‑Aminobutanedioic acid    IUPAC
Aminosuccinic acid    General chemical literature
Aspartate    Biological systems (ionized)
Asparagic acid    Older chemical nomenclature
L‑(+)-Aspartic acid    Optical rotation descriptor
L‑Asp    Biochemical shorthand

Metabolic Roles
Urea cycle: Aspartate donates an amino group during argininosuccinate formation, essential for nitrogen excretion.
TCA cycle: Aspartate interconverts with oxaloacetate, maintaining the cycle's function.
Nucleotide biosynthesis: Aspartate is a key nitrogen donor in purine and pyrimidine synthesis.
Amino acid interconversion: Precursor for asparagine, methionine, threonine, and lysine in microorganisms and plants.

Transport & Compartmentalization
Aspartate is transported across mitochondrial membranes via malate–aspartate shuttle to support NADH transfer and ATP production. 
This shuttle mechanism is critical in tissues with high-energy demands such as brain and heart.

Catabolism
Aspartate is degraded by aspartate ammonia-lyase to fumarate and ammonia or by asparaginase to asparagine, which can be further catabolized.

SAFETY INFORMATION ABOUT L-ASPARTIC ACID

First aid measures:
Description of first aid measures:
General advice:
Consult a physician. 
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
 
If inhaled:
If breathed in, move person into fresh air. 
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off conSAFETYtaminated clothing and shoes immediately. 
Wash off with soap and plenty of water.
Consult a physician.
 
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
 
If swallowed:
Do NOT induce vomiting. 
Never give anything by mouth to an unconscious person. 
Rinse mouth with water. 
Consult a physician.
 
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
 
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment. 
 
Avoid breathing vapours, mist or gas. 
Evacuate personnel to safe areas.
 
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
 
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste. 
Keep in suitable, closed containers for disposal.
 
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
 
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place. 
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
 
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
 
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles. 
Faceshield (8-inch minimum). 
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
 
Skin protection:
Handle with gloves. 
Gloves must be inspected prior to use. 
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product. 
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. 
Wash and dry hands.
 
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
 
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls. 
 
If the respirator is the sole means of protection, use a full-face supplied air respirator. 
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so. 
Do not let product enter drains.
Discharge into the environment must be avoided.
 
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions. 
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
 
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company. 
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product