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Literature summary extracted from

  • Murakawa, T.; Machida, Y.; Hayashi, H.
    Product-assisted catalysis as the basis of the reaction specificity of threonine synthase (2011), J. Biol. Chem., 286, 2774-2784.
    View publication on PubMedView publication on EuropePMC

Cloned(Commentary)

EC Number Cloned (Comment) Organism
4.2.3.1 expression in Escherichia coli Thermus thermophilus

Crystallization (Commentary)

EC Number Crystallization (Comment) Organism
4.2.3.1 apo-protein and in complex with 2-amino-5-phosphonopentanoic acid and with (E)-4-(3-hydroxy-2-methyl-5-(phosphonooxymethyl)pyridin-4-yl)-2-oxobut-3-enoic acid. The enzyme does not undergo any global conformational change upon the binding of pyridoxal 5'-phosphate. The binding of the substrate analog 2-amino-5-phosphonopentanoic acid to the holoenzyme induces a large conformational change from the open to the closed form in which the small domain moves as a rigid body to close the active site. This closed structure is maintained in the complex with (E)-4-(3-hydroxy-2-methyl-5-(phosphonooxymethyl)pyridin-4-yl)-2-oxobut-3-enoic acid, indicating that threonine synthase is in the closed form in the enamine and the pyridoxal 5'-phosphate-alpha-aminocrotonate aldimine intermediates Thermus thermophilus

Organism

EC Number Organism UniProt Comment Textmining
4.2.3.1 Thermus thermophilus Q5SL02
-
-
4.2.3.1 Thermus thermophilus HB8 / ATCC 27634 / DSM 579 Q5SL02
-
-

Reaction

EC Number Reaction Comment Organism Reaction ID
4.2.3.1 O-phospho-L-homoserine + H2O = L-threonine + phosphate the phosphate ion released from O-phospho-L-homoserine by gamma-elimination acts as the base catalyst for the addition of water at Cbeta of the alpha-aminocrotonate aldimine, thereby providing the basis of the reaction specificity. The phosphate ion also accelerates the protonation/deprotonation at Cgamma Thermus thermophilus
a

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4.2.3.1 L-vinylglycine + phosphate + H2O in the presence of phosphate, L-threonine is formed with kcat and reaction specificity comparable with those when O-phospho-L-homoserine is used as the substrate. In the absence of phosphate or when sulfate is used in place of phosphate, only the side reaction product, alpha-ketobutyrate, is formed. Compared with the more acidic sulfate ion, the phosphate ion decreases the energy levels of the transition states of the addition of water at the Cbeta of the PLP-alpha-aminocrotonate aldimine and the transaldimination to form L-threonine. Threonine synthase is in the closed form, when the substrate and the intermediates are bound to the enzyme Thermus thermophilus L-threonine + phosphate
-
 ?
4.2.3.1 L-vinylglycine + phosphate + H2O in the presence of phosphate, L-threonine is formed with kcat and reaction specificity comparable with those when O-phospho-L-homoserine is used as the substrate. In the absence of phosphate or when sulfate is used in place of phosphate, only the side reaction product, alpha-ketobutyrate, is formed. Compared with the more acidic sulfate ion, the phosphate ion decreases the energy levels of the transition states of the addition of water at the Cbeta of the PLP-alpha-aminocrotonate aldimine and the transaldimination to form L-threonine. Threonine synthase is in the closed form, when the substrate and the intermediates are bound to the enzyme Thermus thermophilus HB8 / ATCC 27634 / DSM 579 L-threonine + phosphate
-
 ?
4.2.3.1 O-phospho-L-homoserine + H2O
-
 Thermus thermophilus L-threonine + phosphate reaction is 99% specific for L-threonine formation. Minor product is 2-ketobutanoate ?
4.2.3.1 O-phospho-L-homoserine + H2O
-
 Thermus thermophilus HB8 / ATCC 27634 / DSM 579 L-threonine + phosphate reaction is 99% specific for L-threonine formation. Minor product is 2-ketobutanoate ?

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
4.2.3.1 0.034
-
 phosphate pH 8.0, 25°C Thermus thermophilus
4.2.3.1 0.61
-
 L-Vinylglycine pH 8.0, 25°C Thermus thermophilus
4.2.3.1 0.8
-
 O-phospho-L-homoserine pH 8.0, 25°C Thermus thermophilus

Cofactor

EC Number Cofactor Comment Organism Structure
4.2.3.1 pyridoxal 5'-phosphate
-
 Thermus thermophilus

kcat/KM [mM/s]

EC Number kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
4.2.3.1 0.0013
-
 phosphate pH 8.0, 25°C Thermus thermophilus
4.2.3.1 0.0059
-
 L-Vinylglycine pH 8.0, 25°C Thermus thermophilus
4.2.3.1 5.2
-
 O-phospho-L-homoserine pH 8.0, 25°C Thermus thermophilus