Homoserine
Chemical compound
From Wikipedia, the free encyclopedia
Homoserine (also called isothreonine) is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH2OH. L-Homoserine is not one of the common amino acids encoded by DNA. It differs from the proteinogenic amino acid serine by insertion of an additional −CH2− unit into the sidechain. Homoserine, or its lactone, is the product of a cyanogen bromide cleavage of a peptide by degradation of methionine. Homoserine is an intermediate in the biosynthesis of three essential amino acids: methionine, threonine (an isomer of homoserine), and isoleucine.[1]
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| Names | |
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| IUPAC name
(S)-2-Amino-4-hydroxybutanoic acid | |
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3D model (JSmol) |
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| ECHA InfoCard | 100.010.538 |
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CompTox Dashboard (EPA) |
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| Properties | |
| C4H9NO3 | |
| Molar mass | 119.12 g/mol |
| Melting point | 203 °C (decomposes) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Applications
Commercially, homoserine can serve as precursor to the synthesis of isobutanol and 1,4-butanediol.[2] Purified homoserine is used in enzyme structural studies.[3] Also, homoserine has played important roles in studies to elucidate peptide synthesis and synthesis of proteoglycan glycopeptides.[4] Bacterial cell lines can make copious amounts of this amino acid.[5][2]
Biosynthesis
Its complete biosynthetic pathway includes glycolysis, the tricarboxylic acid (TCA) or citric acid cycle (Krebs cycle), and the aspartate metabolic pathway.[clarification needed] It forms by two reductions of aspartic acid via the intermediacy of aspartate semialdehyde.[6] Specifically, the enzyme homoserine dehydrogenase, in association with NADPH, catalyzes a reversible reaction that interconverts L-aspartate-4-semialdehyde to L-homoserine. Homoserine kinase and homoserine O-succinyltransferase convert homoserine to phosphohomoserine and O-succinyl homoserine, respectively.[5] Homoserine is produced from aspartate via the intermediate aspartate-4-semialdehyde, which is produced from β-phosphoaspartate. By the action of homoserine dehydrogenases, the semialdehyde is converted to homoserine.[7]
Other biochemical roles
L-Homoserine is substrate for homoserine kinase, yielding phosphohomoserine (homoserine-phosphate), which is converted by threonine synthase to L-threonine.
Homoserine is converted to O-succinyl homoserine by homoserine O-succinyltransferase. O-succinyl homoserine is a precursor to L-methionine.[8]
Homoserine inhibits aspartate kinase and glutamate dehydrogenase.[5] Glutamate dehydrogenase reversibly converts glutamate to α-ketoglutarate and α-ketoglutarate coverts to oxaloacetate through the citric cycle. Threonine acts as another allosteric inhibitor of aspartate kinase and homoserine dehydrogenase, but it is a competitive inhibitor of homoserine kinase.[8]
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