All Topics  
Threonine

 

 
   Email Print
   Bookmark   Link
 

 

Threonine
 
 
  Topics Threonine Topic Home

Threonine (abbreviated as Thr or T) is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 with the chemical formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HO2CCH(NH2)CH(OH)CH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid
Essential amino acid

File:BakedFish.jpgAn essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo synthesis by the organism , and therefore must be supplied in the diet....
 is classified as polar
Chemical polarity

In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly electric charge end of one molecule to the negative end of another or the same molecule....
. Together with serine
Serine

Serine is an organic compound with the chemical formula hydrogenoxygen2carbonCHCH2OH....
 and tyrosine
Tyrosine

Tyrosine or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cell to protein biosynthesis proteins. This is a non-essential amino acid and it is found in casein....
, threonine is one of three proteinogenic amino acids bearing an alcohol
Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
 group.

The threonine residue is susceptible to numerous posttranslational modification
Posttranslational modification

Posttranslational modification is the chemistry modification of a protein after its translation . It is one of the later steps in protein biosynthesis for many proteins....
s. The hydroxy
Hydroxy

'Hydroxy' can refer to:* In chemical nomenclature, the prefix "hydroxy-" shows the presence of a hydroxyl functional group * An abbreviation for the medication hydroxyzine, which is commonly sold under the brand names Atarax, Ucerax, Serecid, and Vistaril....
 side chain
Side chain

A side chain in organic chemistry and biochemistry is a part of a molecule that is attached to a core structure. The placeholder R is often used as a generic placeholder for side chains, the R historically being derived from radical or rest....
 can undergo O-linked glycosylation
Glycosylation

Glycosylation is the enzymatic process that links saccharides to produce glycans, either free or attached to proteins and lipids. This enzymatic process produces one of four fundamental components of all cells and also provides a co-translational and post-translational modification mechanism that modulates the structure and function of membr...
.






Discussion
Ask a question about 'Threonine'
Start a new discussion about 'Threonine'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Threonine (abbreviated as Thr or T) is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 with the chemical formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HO2CCH(NH2)CH(OH)CH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid
Essential amino acid

File:BakedFish.jpgAn essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo synthesis by the organism , and therefore must be supplied in the diet....
 is classified as polar
Chemical polarity

In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly electric charge end of one molecule to the negative end of another or the same molecule....
. Together with serine
Serine

Serine is an organic compound with the chemical formula hydrogenoxygen2carbonCHCH2OH....
 and tyrosine
Tyrosine

Tyrosine or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cell to protein biosynthesis proteins. This is a non-essential amino acid and it is found in casein....
, threonine is one of three proteinogenic amino acids bearing an alcohol
Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
 group.

The threonine residue is susceptible to numerous posttranslational modification
Posttranslational modification

Posttranslational modification is the chemistry modification of a protein after its translation . It is one of the later steps in protein biosynthesis for many proteins....
s. The hydroxy
Hydroxy

'Hydroxy' can refer to:* In chemical nomenclature, the prefix "hydroxy-" shows the presence of a hydroxyl functional group * An abbreviation for the medication hydroxyzine, which is commonly sold under the brand names Atarax, Ucerax, Serecid, and Vistaril....
 side chain
Side chain

A side chain in organic chemistry and biochemistry is a part of a molecule that is attached to a core structure. The placeholder R is often used as a generic placeholder for side chains, the R historically being derived from radical or rest....
 can undergo O-linked glycosylation
Glycosylation

Glycosylation is the enzymatic process that links saccharides to produce glycans, either free or attached to proteins and lipids. This enzymatic process produces one of four fundamental components of all cells and also provides a co-translational and post-translational modification mechanism that modulates the structure and function of membr...
. In addition, threonine residues undergo phosphorylation
Phosphorylation

Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Protein phosphorylation in particular plays a significant role in a wide range of cellular processes....
 through the action of a threonine kinase
Kinase

In chemistry and biochemistry, a kinase, alternatively known as a phosphotransferase, is a type of enzyme that transfers phosphate groups from High-energy phosphate donor molecules, such as adenosine triphosphate, to specific target molecules ; the process is termed phosphorylation ...
. In its phosphorylated form, it can be referred to as phosphothreonine.

Allo-threonine

With two chiral
Chirality (chemistry)

The term chiral is used to describe an object that is non-Superposition on its mirror image.Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands...
 centers, threonine can exist in four possible stereoisomers, or two possible diastereomer
Diastereomer

Diastereomers are stereoisomers that are not enantiomers . Diastereomers can have different physical properties and different reactivity. In another definition diastereomers are pairs of isomers that have opposite configurations at one or more of the chiral centers but are not mirror images of each other ....
s of L-threonine. However, the name L-threonine is used for one single enantiomer
Enantiomer

In chemistry, an enantiomer is one of two stereoisomers that are Superpose complete mirror images of each other, much as one's left and right Chirality are "the same" but opposite....
, (2S,3R)-2-amino-3-hydroxybutanoic acid. The second diastereomer (2S,3S), which is rarely present in nature, is called L-allo-threonine.

Biosynthesis

As an essential amino acid, threonine is not synthesized in humans, hence we must ingest threonine in the form of threonine-containing proteins. In plants and microorganisms, threonine is synthesized from aspartic acid
Aspartic acid

Aspartic acid is an a-amino acid with the chemical formula HO2CCHCH2CO2H. The carboxylate anion of aspartic acid is known as aspartate....
 via a-aspartyl-semialdehyde and homoserine
Homoserine

Homoserine is an a-amino acid with the chemical formula HO2CCHCH2CH2OH. L-Homoserine is not one of the common amino acids encoded by DNA....
. Homoserine undergoes O-phosphorylation; this phosphate ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
 undergoes hydrolysis concomitant with relocation of the OH group. Enzymes involved in a typical biosynthesis of threonine include:
  1. aspartokinase
    Aspartokinase

    Aspartokinase is an enzyme that catalysis the phosphorylation of the amino acid aspartate. This reaction is the first step in the biosynthesis of three essential amino acids: methionine, lysine, and Threonine, known as the "aspartate family"....
  2. a-aspartate semialdehyde dehydrogenase
    Dehydrogenase

    A dehydrogenase is an enzyme that oxidizes a substrate by transferring one or more hydrides to an acceptor, usually Nicotinamide adenine dinucleotide/NADP or a flavin coenzyme such as FAD or FMN....
  3. homoserine dehydrogenase
  4. homoserine kinase
    Kinase

    In chemistry and biochemistry, a kinase, alternatively known as a phosphotransferase, is a type of enzyme that transfers phosphate groups from High-energy phosphate donor molecules, such as adenosine triphosphate, to specific target molecules ; the process is termed phosphorylation ...
  5. threonine synthase
    Synthase

    In biochemistry, a synthase is an enzyme which catalyzes a synthesis process.Following the EC number classification, they belong to the group of ligases, with lyases catalysing the reverse reaction....
    .


Thr Biosynthesis

Metabolism

Threonine is metabolized in two ways:
  • It is converted to pyruvate via threonine dehydrogenase. An intermediate in this pathway can undergo thiolysis
    Thiolysis

    Thiolysis is a reaction with a thiol that cleaves one compound into two. This reaction is similar to hydrolysis, which involves water instead of a thiol. This reaction is seen in beta-oxidation of fatty acids....
     with CoA to produce Acetyl-CoA
    Acetyl-CoA

    Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidation for energy production....
     and glycine
    Glycine

    Glycine is the organic compound with the chemical formula NH2CH2COOH. It is the smallest of the 20 amino acids commonly found in proteins, coded by codons GGU, GGC, GGA and GGG....
    .
  • In humans, it is converted to alpha-ketobutyrate in a less common pathway via the enzyme serine dehydratase
    Serine dehydratase

    Serine dehydratase is an enzyme which converts serine to pyruvate.It also converts Threonine to Propionyl CoA.External links...
    , and thereby enters the pathway leading to succinyl-CoA
    Succinyl-CoA

    Succinyl-Coenzyme A, generally abbreviated as Succinyl-CoA or SucCoA is a combination of succinic acid and coenzyme A....
    .


Sources

Foods high in threonine include cottage cheese
Cottage cheese

Cottage cheese is a cheese curd product with a mild flavor. It is drained, but not pressed so some whey remains. The curd is usually washed to remove acidity giving sweet curd cheese....
, poultry
Poultry

Poultry is the category of domesticated birds which some people keep for the purpose of collecting their egg , or kill for their meat and/or feathers....
, fish
Fish

A fish is any marine biology vertebrate animal that is typically ectothermic , covered with scale , and equipped with two sets of paired fins and several unpaired fins....
, meat
Meat

In modern English usage, meat most often refers to animal biological tissue used as food, mostly skeletal muscle and associated fat, but it may also refer to offal, including livers, skin, brains, bone marrow, kidneys, in some countries lungs, and a variety of other internal organs as well as blood....
, lentil
Lentil

The lentil or daal or pulse is a bushy annual plant of the Fabaceae family, grown for its lens-shaped seeds. It is about 15 inches tall and the seeds grow in pods, usually with two seeds in each....
s, and sesame seeds.

Racemic
Racemic

In chemistry, a racemic mixture, or racemate, is one that has equal Amount of substance of left- and right-handed enantiomer of a Chirality molecule....
 threonine can be prepared from crotonic acid
Crotonic acid

Crotonic acid, or trans-2-butenoic acid, is a short-chain unsaturated compound carboxylic acid, described by the formula CH3CH=CHCO2H....
 by alpha-functionalization using mercury(II) acetate
Mercury(II) acetate

Mercury acetate is the chemical compound with the chemical formula Mercury 2. Commonly abbreviated Hg2, this compound is employed as a reagent to generate organomercury compounds from unsaturated organic precursors....
.

See also

  • H.E. Carter in collaboration with William C. Rose first determined the structure of threonine
  • Harold Dadford West
    Harold Dadford West

    Harold Dadford West was an United States Biochemistry who was the the first to synthesize threonine....
     American Biochemist who first synthetised the Threonine.


External links