Threonine

Threonine (abbreviated as Thr or T)^[1] is an α-tyrosine, threonine is one of three proteinogenic amino acids bearing an alcohol group.

The threonine residue is susceptible to numerous kinase. In its phosphorylated form, it can be referred to as phosphothreonine.

Allo-threonine

With two enantiomer, (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 ester undergoes hydrolysis concomitant with relocation of the OH group.^[2] Enzymes involved in a typical biosynthesis of threonine include:

1. aspartokinase
2. α-aspartate semialdehyde dehydrogenase
3. homoserine dehydrogenase
4. homoserine kinase
5. threonine synthase.

Metabolism

Threonine is metabolized in two ways:

• It is converted to pyruvate via Threonine Dehydrogenase. An intermediate in this pathway can undergo thiolysis with CoA to produce Acetyl-CoA and glycine.
• In humans, it is converted to alpha-ketobutyrate in a less common pathway via the enzyme Serine dehydratase, and thereby enters the pathway leading to succinyl-CoA.

Sources

Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, and sesame seeds.^{[citation needed]}

crotonic acid by alpha-functionalization using mercury(II) acetate.^[3]

References

1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides. Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. Retrieved on 2007-05-17.
2. ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
3. ^ Carter, H. E.; West, H. D. (1955). "dl-Threonine". Org. Synth.; Coll. Vol. 3: 813.