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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 ?
As recently demonstrated (10), the processing of human proBNP is inhibited by O-glycosylation of the threonine 71 residue located close to the cleavage site.
The candidates, serine, threonine, arginine, asparagine, lysine, histidine, tyrosine, glutamine, and cysteine as well as glycine, as a negative control, were analyzed.
Observations of an On-Face Hydrogen Bond Between the Side-Chain of Threonine 13 and the [pi]-Cloud of Tyrosine 6 and Its Influence on Catalysis, J.
However, considering the lack of additivity of value for AID [17] and the statistical criterion of [R.sup.2], RMSE and AIC, prediction equations 7, 9, and 11 appear useful to evaluate the SID of lysine, threonine and valine in SBM.
The signals of alanine threonine valine acetate fumaric acid glutamate glutamine adenine gallic acid malic acid and GABA were detected in the spectral region of organic and amino acids.
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.
What the young research has revealed already, however, is that the ability of TD2 to break down threonine is activated only after it enters the insect's gut in the form of a chewed up leaf.
However, alignment of 439 [alpha]-globin sequences from different species shows that residue [alpha]82 is only loosely conserved as alanine, and some 18 species, including mouse and rabbit, have a threonine residue at position [alpha]82.
Methods for their use to produce increased levels of lysine or threonine in the seeds of transformed plants are provided.
We amplified the ctxB gene using specific primers and found that the deduced amino acid sequence of the CT-B subunit of the Mozambique strains varied from the El Tor CT-B subunit at positions 39 (histidine replaces tyrosine in El Tor) and 68 (threonine replaces isoleucine in El Tor), and the amino acid residues at these positions are identical to those of the classical CTB subunit (Figure).