4.2.1.122: tryptophan synthase (indole-salvaging)
This is an abbreviated version!
For detailed information about tryptophan synthase (indole-salvaging), go to the full flat file.
Reaction
Synonyms
PfTrpB, PfTrpS, StTrpS (beta2), Trp synthase, TrpB2, TrpBbeta, TRPS, tryptophan synthase
ECTree
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Substrates Products
Substrates Products on EC 4.2.1.122 - tryptophan synthase (indole-salvaging)
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REACTION DIAGRAM
L-serine + 4-hydroxyindole
4-hydroxy-L-tryptophan + H2O
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-
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?
L-serine + 5-hydroxyindole
5-hydroxy-L-tryptophan + H2O
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-
-
?
L-serine + 7-hydroxyindole
7-hydroxy-L-tryptophan + H2O
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-
-
?
L-threonine + 2-methylindole
(2S,3S)-2-methyl-beta-methyltryptophan + H2O
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-
-
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?
L-threonine + 4-fluoroindole
(2S,3S)-4-fluoro-beta-methyltryptophan + H2O
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-
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?
L-threonine + 4-methylindole
(2S,3S)-4-methyl-beta-methyltryptophan + H2O
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-
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?
L-threonine + 5-bromoindole
(2S,3S)-5-bromo-beta-methyltryptophan + H2O
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-
-
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?
L-threonine + 5-chloroindole
(2S,3S)-5-chloro-beta-methyltryptophan + H2O
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-
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?
L-threonine + 5-phenylindole
(2S,3S)-5-phenyl-beta-methyltryptophan + H2O
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-
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?
L-threonine + 6-methylindole
(2S,3S)-6-methyl-beta-methyltryptophan + H2O
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-
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?
L-threonine + 7-azaindole
(2S,3S)-2-amino-3-(1H-pyrrolo[2,3-b]pyridin-3-yl)butanoic acid + H2O
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engineered mutant enzyme PfTrpB2B9
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?
L-threonine + 7-chloroindole
(2S,3S)-7-chloro-beta-methyltryptophan + H2O
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?
L-threonine + 7-fluoroindole
(2S,3S)-7-fluoro-beta-methyltryptophan + H2O
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-
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?
L-threonine + 7-methoxyindole
(2S,3S)-7-methoxy-beta-methyltryptophan + H2O
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-
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?
L-threonine + 7-methylindole
(2S,3S)-7-methyl-beta-methyltryptophan + H2O
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-
-
-
?
L-serine + indole
L-tryptophan + H2O
L-serine is the preferred substrate
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?
L-serine + indole
L-tryptophan + H2O
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L-serine is the preferred substrate
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?
L-serine + indole
L-tryptophan + H2O
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Ser and IGP react with a coupling efficiency of over 99% and only trace indole is released into solution by cells
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?
L-serine + indole
L-tryptophan + H2O
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L-serine is the preferred substrate
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?
L-serine + indole
L-tryptophan + H2O
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the enzyme is involved in L-tryptophan biosynthesis. TrpB2 does not interact with TrpA as in the case of TrpB1. TrpB2 provides an alternate route to generate Trp from serine and free indole (indole salvage)
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?
(2S,3S)-beta-methyltryptophan + H2O
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?
L-threonine + indole
(2S,3S)-beta-methyltryptophan + H2O
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only 17% of the indole that is released from the alpha-subunit goes on to form beta-MeTrp, demonstrating that the release of indole is decoupled from product formation. Thr binds non-covalently to the isolated beta-subunit, indicating that the beta-methyl group hinders entry into the catalytic cycle. The beta-methyl of Thr causes a steric clash that destabilizes the E(Aex1) intermediate
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?
L-threonine + indole
(2S,3S)-beta-methyltryptophan + H2O
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veryl low activity of the wild-type enzyme, higher activity with engineered mutant enzymes
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?
L-threonine + indole
(2S,3S)-beta-methyltryptophan + H2O
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?
?
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enzymatic production of psilocybin formation from 4-hydroxyindole and L-serine and of 7-phosphoryloxytryptamine (isonorbaeocystin), a non-natural congener of the Psilocybe alkaloid norbaeocystin (4-phosphoryloxytryptamine), and of serotonin (5-hydroxytryptamine) by means of the same in vitro approach, overview
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additional information
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the rate of Thr deamination by PfTrpS is 8.5fold faster than with Ser, competitive with the rate of beta-substitution. Substrate differentiation mechanism of the enzyme, molecular dynamics simulations analysis, overview
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additional information
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beta-substitution occurs in vitro with a 3.4fold higher catalytic efficiency for Ser over Thr using saturating indole, despite over 82000fold preference for Ser in direct competition using IGP. When the reaction is conducted with a 1000fold molar excess of Thr over Ser, only Trp is observed, with no trace of beta-MeTrp. Atypical mechanism of specificity: Thr binds efficiently but decreases the affinity for indole and disrupts the allosteric signaling that regulates the catalytic cycle
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additional information
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no activity of engineered mutant enzyme with 5-chloro-, 5-bromo, and 6-hydroxyindoles combined with L-threonine
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additional information
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activity and isolated yields of L-beta-methyl-Trp are low compared to the wild-type reaction with l-Ser, which gives over 90% of L-Trp under the same conditions. Preperative scale synthesis (2S,3S)-L-beta-methyl tryptophan and derivatives
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additional information
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TrpB2 does not bind to TrpA but is catalytically highly active, has an extremely low Km value for indole
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