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(thrē`ənēn), organic compound, one of the 22 α-amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. It is one of several essential amino acids needed in the diet; human beings cannot synthesize it from simpler metabolites. Young adults need about 14 mg of this amino acid per day per kilogram (6 mg per lb) of body weight. Although threonine participates in many reactions in bacteria, including the biosynthesis of vitamin B12 and isoleucineisoleucine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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, its metabolic role in higher animals, including man, remains obscure. It is known only as a constituent of proteins, and even in that form it is relatively unreactive. In spite of the fact that its side chain has a hydroxyl group similar to that of serineserine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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, there is no indication that it participates in the catalytic functions of any enzyme. Threonine was isolated from the protein fibrin in 1935 and synthesized in the same year.



α-amino-β-hydroxybutyric acid, a natural amino acid, CH3CH(OH)CH(NH2)COOH. It exists in four optically active forms and two racemates (L-, D-, and DL-threonine and L-, D-, and DL-allothreonine). Natural L-threonine was isolated in 1935 from acid hydrolysates of fibrin. L-threonine constitutes 2–6 percent of all natural proteins, except protamines.

Threonine is an essential amino acid. The daily requirement for adults is 0.5 g, and for children up to the age of 7, about 3 g. The precursor of L-threonine during biosynthesis in plants and microorganisms is aspartic acid. This multistage enzymic process is regulated according to the feedback principle: excess threonine inhibits the first enzyme on the path to the biosynthesis of threonine. There are various possible pathways for the decomposition of threonine in the body; they lead to the formation of a-ketobutyric acid, acetaldehyde, and glycine, as well as pyruvic acid.

A method for the chemical synthesis of L-threonine from acetaldehyde and glycine has been developed.


Meister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)



CH3CHOHCH(NH2)COOH A crystalline α-amino acid considered essential for normal growth of animals; it is biosynthesized from aspartic acid and is a precursor of isoleucine in microorganisms.
References in periodicals archive ?
The breakpoints for post-prandial plasma free threonine concentrations (PPthr), post-absorptive free threonine concentrations (PAthr) and post-prandial plasma ammonia concentrations (PPA) were estimated by using the broken line model of Robbins et al.
First, in the FFD muscles following taurine supplementation for 2 weeks, there was a common phenomenon to decreased concentrations of the pyruvate precursor amino acids; threonine, serine, and glycine, rather than amino acids categorized into other gluconeogenesis pathways.
Gilliland, Crystallographic, Molecular Modeling and Biophysical Characterization of Valine (67) (E11)[beta] Threonine Variant of Hemoglobin, Biochemistry 35 (6), 1935-1945 (1996).
A total of 450 21-d-old ducklings were fed one of five diets with varying levels of lysine, TSAA and threonine with consistent balance (T1: 0.
Apart from threonine which is being produced for sale, the Group will use its fermentation technology to develop and produce other new biochemical products, including other high value-added amino acid products.
Some important feed amino acids include Tryptophan, Lysine, Methionine, Threonine, and Others.
MSG products include MSG, glutamic acid, fertilizers, corn refined products, starch sweeteners, threonine, corn oil, branched-chain amino acid and chicken powder.
Tokyo, Japan) has patented transgenic plants containing free amino acids, particularly at least one amino acid selected from among glutamic acid, asparagine, aspartic acid, serine, threonine, alanine and histidine accumulated in a large amount, in edible parts thereof, and a method of producing them.
An example is the repetition of a threonine residue within the VR2 P1.
The protein contains an abundance of specific amino acids, such as serine and threonine, that have "sticky" chemical appendages known as hydroxyl groups, which consist of an oxygen and a hydrogen atom.
Such premix formulas typically contain vitamins and minerals, amino acids such as lysine and threonine, and other ingredients.