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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 ?
In summary, under the conditions of this experiment, the ileal digestibility of lysine, threonine, valine, cysteine, glycine and proline in SBM from China was greater than in SBM from Brazil.
Thus, the results give reason to believe that the use of Ion-Ozone processing in the cavitations zone has a positive impact on the quality of winter wheat--namely, increase in the content of lysine and threonine in the grain and improvement in the overall biochemical properties of grain processing.
There are relatively few studies conducted to evaluate the marginal efficiency of threonine utilization by pigs.
The mushrooms were poor in valine, threonine, leucine and methionine (or cysteine).
The colonies that had grown on bactocasamino acids were then restreaked on glutamate agar, glutamate-alanine agar, alanine agar, homoserine agar, homoserine-glutamate agar and homoserine-alanine agar from first experiment and on methionine, threonine, alanine, homoserine- alanine, methionine-alanine, threonine-alanine, methionine-threonine and methionine-threonine- alanine agar from the 2nd experiment of bactocasamino acid agar and on leucine agar from the 3rd experiment.
Following taurine supplementation for 2 weeks, the pyruvate precursor amino acids; threonine (p < 0.
The anhydrides were predicted to react with the amino acid side chains of serine, threonine, arginine, asparagine, lysine, histidine, tyrosine, glutamine, and cysteine.
Threonine requirement of healthy adults, derived with a 24-h indicator amino acid balance technique.
The insertion in the HA protein sequence from the Fraser Valley isolates does not conform to the consensus motif (R-X-R/K-R*-G-L-F) for an HA1 HA2 connecting peptide in HPAI viruses because a threonine is at the -2 position.
plant for feed-use threonine in Eddyville, Iowa, to 20,000 tons a year.