One of the 20 amino acids that make up proteins.



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Threonine C₄H₉NO₃


Molar mass: 119.12 g/mol

Melting point: 255 °C (491 °F)

Density: 1.671 g/cm³ (0.0604 lb/in³)


Threonine is an essential amino acid, which is indispensable for both humans and animals. Since it cannot be produced in the body, it must be obtained from food. It is a colorless, crystalline substance, easily soluble in water, but insoluble in alcohol, ether or chloroform.

Occurrence and production

Threonine occurs both in its free form and as a building block of proteins. Dietary sources include meat, lentils and sesame seeds. In plants and microorganisms, biosynthesis of threonine proceeds from aspartic acid.


For adults, the recommended daily intake of threonine is 0.5 grams (0.0176 ounces). It plays an important role in fat metabolism; a threonine deficiency may lead to a buildup of fat in the liver and cirrhosis of the liver.

Threonine is also used in animal feed and in synthetic dietary supplements.

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Amino acids

Amino acids are the monomers of proteins.

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