Valine
Properties
| State | Solid (white crystalline powder) |
| Color | White |
| Solubility | Soluble in water (88 g/L at 25°C); slightly soluble in ethanol |
| Melting Point | 298°C (decomposes) |
| Boiling Point | Decomposes before boiling |
About Valine
Valine is one of the three branched-chain amino acids (BCAAs), grouped with leucine and isoleucine by their hydrophobic side chains and by a metabolic peculiarity: BCAAs are catabolized primarily in skeletal muscle rather than the liver, because muscle expresses the rate-limiting branched-chain alpha-ketoacid dehydrogenase complex (BCKDH) at much higher levels than hepatic tissue. Valine itself was first isolated from valerian root by Emil Fischer in 1901 (which is where the name comes from), and its isopropyl side chain makes it strongly hydrophobic — it appears at high frequency in the buried cores of globular proteins and at the dimerization interfaces of leucine zippers and coiled coils. The single most consequential valine in human biology is the one at position 6 of the beta-globin chain in hemoglobin S, where a single A->T mutation in codon 6 (GAG -> GTG) substitutes valine for the normal glutamic acid. The hydrophobic Val patch on one beta-globin then docks into a hydrophobic pocket on a neighboring deoxygenated hemoglobin, polymerizing the molecules into long fibers that deform red cells into the rigid sickled shape responsible for sickle cell disease. This was the first molecular disease ever identified — Linus Pauling and Harvey Itano's 1949 paper "Sickle Cell Anemia, a Molecular Disease" — and remains the textbook example of how a single amino acid substitution can have systemic consequences. In clinical nutrition, valine plus the other BCAAs is given to patients with hepatic encephalopathy to correct the abnormal aromatic-to-branched amino acid ratio that develops in advanced liver failure.
Where you'll encounter it
If you have ever scooped a BCAA powder into a shaker bottle after a workout, the typical 2:1:1 leucine:isoleucine:valine ratio in the formulation traces back to leucine being the strongest mTOR activator and the BCAA most strongly tied to muscle protein synthesis — valine and isoleucine ride along to keep the catabolic balance from skewing. In a clinical setting, BCAA-enriched parenteral nutrition (Aminosyn-HBC or Hepatamine) is infused into cirrhotic patients with grade 2-4 hepatic encephalopathy where the disturbed ammonia metabolism and altered BCAA-to-AAA ratio at the blood-brain barrier contributes to the neurological symptoms. The most catastrophic valine-related condition is maple syrup urine disease (MSUD), a rare autosomal recessive disorder caused by mutations in BCKDH; without rapid neonatal detection by tandem MS screening (which has been routine in US states since the early 2000s) and lifelong dietary BCAA restriction, infants accumulate toxic alpha-ketoacids in the first week of life, with the characteristic burnt-sugar-smelling urine that gave the disease its name and progressive encephalopathy that was uniformly fatal before screening programs.
Common Uses
- Essential dietary amino acid supplied at 24-26 mg/kg/day adult requirement per WHO/FAO/UNU standards
- Component of BCAA supplements at 2:1:1 leucine:isoleucine:valine ratio for athletic recovery and muscle protein synthesis
- Active ingredient in BCAA-enriched parenteral nutrition formulations for hepatic encephalopathy patients
- Reference amino acid in textbook explanations of sickle cell disease E6V hemoglobin mutation
- Substrate in industrial fermentation routes producing pantothenic acid (vitamin B5) precursors
- Reagent in solid-phase peptide synthesis using Fmoc-Val-OH building blocks for therapeutic peptide manufacture
- Cell culture media component in CHO and HEK293 fed-batch processes for monoclonal antibody production
- Calibration standard in amino acid analyzers using ninhydrin or OPA post-column derivatization detection
Safety Information
Valine is GRAS for dietary use under FDA regulations and not classified as hazardous under GHS for laboratory handling, with no OSHA PEL established. Acute oral toxicity is minimal (rat LD50 above 5,000 mg/kg). The clinically relevant safety issue is maple syrup urine disease (MSUD), an autosomal recessive disorder of branched-chain alpha-ketoacid dehydrogenase that causes valine, leucine, and isoleucine to accumulate to neurotoxic levels in untreated patients; tandem mass spectrometry newborn screening detects MSUD in the first week of life, and lifelong dietary BCAA restriction prevents the encephalopathy. For typical adults consuming BCAA supplements above 20 g/day, watch for elevated ammonia and impaired glucose tolerance in susceptible individuals. Standard lab handling of valine powder uses nitrile gloves and a dust mask for bulk weighing; no special engineering controls are required for ordinary research-scale work.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.