L-Threonine

L‑Threonine is an essential, protein‑building amino acid that humans must obtain from the diet because the body cannot synthesize it in sufficient quantities. It plays a central role in protein synthesis, collagen formation, and the production of critical biomolecules such as glycine, serine, and the neurotransmitter acetylcholine, supporting a wide range of physiological processes.

• Chemical Name: L‑Threonine (L‑2‑amino‑3‑hydroxy‑butanoic acid)
• Molecular Formula: C₄H₉NO₃
• Molecular Weight: 119.12 g mol⁻¹
• IUPAC Name: (2S)-2‑amino‑3‑hydroxybutanoic acid
• Structure: The molecule features a chiral α‑carbon (S‑configuration) bearing an amino group, a carboxylic acid, and a side‑chain hydroxyl group, which confers polarity and solubility in water (≈ 100 g L⁻¹ at 25 °C).
• Distinguishing Feature: The presence of the β‑hydroxyl group distinguishes threonine from serine and allows participation in hydrogen‑bonding networks in proteins, often stabilizing α‑helices.
• pKa Values: The pKa values are ~2.3 (carboxyl) and ~9.1 (α‑amino), giving an isoelectric point near 5.6.
• Stability: The compound is stable under neutral pH but can undergo oxidation via the hydroxyl group under harsh conditions.

• Production Method: Commercial L‑threonine is primarily produced fermentatively using genetically engineered Corynebacterium glutamicum or Escherichia coli strains that overproduce the amino acid from glucose or molasses.
• Processing: Fermentation yields a high‑purity (>99 %) product that is later crystallized and milled to a fine powder.
• Natural Sources: Natural dietary sources include dairy, eggs, meat, and some legumes (e.g., soy, lentils), where threonine is part of the protein matrix.
• Supplement Grades: For supplements, food‑grade and pharmaceutical‑grade specifications differ; the latter requires stringent testing for microbial contamination, heavy metals, and residual solvents.
• Quality Markers: Certified‑organic or non-GMO labels are common quality markers.
• Supplement Selection: When selecting a supplement, look for GMP‑certified manufacturers, third‑party testing (e.g., USP, NSF), and clear labeling of free‑form vs. “bound” threonine to ensure bioavailability and purity.