L-Alanine
[CAS# 56-41-7]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon halide
• Name: L-Alanine
• Synonyms: L-2-Aminopropanoic acid; Ala
• Molecular Formula: C₃H₇NO₂
• Molecular Weight: 89.09
• Protein Sequence: A
• CAS Registry Number: 56-41-7
• EC Number: 200-273-8
• SMILES: C[C@@H](C(=O)O)N

Properties

• Melting point: 314-316 °C
• alpha: 14.5 ° (c=10,6N HCl,dry sub.)
• Water solubility: 166.5 g/L (25 °C)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2A	H319
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

L-Alanine is one of the 20 standard α-amino acids commonly found in proteins. It has the chemical formula C₃H₇NO₂ and a molecular structure consisting of a central α-carbon atom bonded to an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and a methyl side chain (–CH₃). The methyl group makes alanine a nonpolar, aliphatic amino acid. L-Alanine is the naturally occurring enantiomer and is coded in proteins by the genetic codons GCU, GCC, GCA, and GCG.

The discovery of alanine dates back to the 19th century. It was first isolated in the mid-1800s through the hydrolysis of proteinaceous materials. The name "alanine" is derived from the aldehyde "acetaldehyde," due to early hypotheses regarding its structure. It was among the early amino acids to be structurally characterized and studied for its role in protein composition.

L-Alanine is a non-essential amino acid for humans, meaning that it can be synthesized by the body and does not need to be obtained through the diet. In animals, L-alanine is synthesized primarily from pyruvate by transamination reactions. The enzyme alanine aminotransferase (ALT) catalyzes the reversible conversion between pyruvate and L-alanine, using glutamate as the amino donor. This reaction is significant in nitrogen metabolism and is also a key part of the glucose-alanine cycle between muscle and liver.

One of the important physiological roles of L-alanine is its function in the transport of amino groups and carbon skeletons in peripheral tissues to the liver, where gluconeogenesis occurs. In this process, muscle cells generate alanine by transferring amino groups to pyruvate; the alanine then travels through the bloodstream to the liver, where it is deaminated back to pyruvate for glucose production. This helps maintain blood glucose levels during periods of fasting or strenuous activity.

L-Alanine is abundant in many proteins and tends to be found in α-helical regions due to its small side chain, which imposes minimal steric hindrance. Its nonpolar nature contributes to protein folding by stabilizing hydrophobic interactions in the interior of proteins. In structural biology, alanine scanning mutagenesis is often used to investigate the role of individual amino acids in proteins by systematically replacing them with alanine.

Beyond its presence in proteins, L-alanine also finds application in food, pharmaceutical, and biochemical industries. It is used as a component of intravenous nutrition solutions, a flavor enhancer in food products due to its slightly sweet taste, and as a building block for the synthesis of peptides and other biomolecules. In biochemical assays, it is used as a standard amino acid for calibration and research.

Clinically, alanine transaminase (ALT) activity in the blood is measured as a diagnostic marker for liver health. Elevated ALT levels are commonly associated with liver damage or inflammation, such as in hepatitis or drug-induced liver injury.

In microbial metabolism, L-alanine is synthesized by bacteria and other microorganisms and incorporated into structural components such as peptidoglycan, particularly in Gram-positive bacteria, where D-alanine (produced from L-alanine by racemization) is used for cell wall cross-linking.

In summary, L-alanine is a naturally occurring α-amino acid essential to protein structure and energy metabolism. It plays a vital role in glucose regulation, protein biosynthesis, and nitrogen transport, and is used in various scientific, medical, and industrial contexts.

References

2025. Synthesis of Yellow Fluorescence Carbon Dots for the Applications of Vitamin B12 Detection and Cell Imaging. Journal of Fluorescence, 35(2).
DOI: 10.1007/s10895-023-03558-9

2025. Alanine metabolism mediates energy allocation of the brown planthopper to adapt to resistant rice. Journal of Advanced Research, 55.
DOI: 10.1016/j.jare.2024.01.022

2024. Chiral recognition of amino acids through homochiral metallacycle [ZnCl2L]2. Biomaterials Science, 12(24).
DOI: 10.1039/d4bm01119h