Information on EC 4.2.1.122 - tryptophan synthase (indole-salvaging)

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The expected taxonomic range for this enzyme is: Archaea, Bacteria

EC NUMBER
COMMENTARY
4.2.1.122
-
RECOMMENDED NAME
GeneOntology No.
tryptophan synthase (indole-salvaging)
-
REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
L-serine + indole = L-tryptophan + H2O
show the reaction diagram
-
-
-
-
PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
L-tryptophan biosynthesis
-
-
NIL
-
-
SYSTEMATIC NAME
IUBMB Comments
L-serine hydro-lyase [adding indole, L-tryptophan-forming]
Most mesophilic bacteria have a multimeric tryptophan synthase complex (EC 4.2.1.20) that forms L-tryptophan from L-serine and 1-C-(indol-3-yl)glycerol 3-phosphate via an indole intermediate. This intermediate, which is formed by the alpha subunits, is transferred in an internal tunnel to the beta units, which convert it to tryptophan. In thermophilic organisms the high temperature enhances diffusion and causes the loss of indole. This enzyme, which does not combine with the alpha unit to form a complex, salvages the lost indole back to L-tryptophan. It has a much lower Km for indole than the beta subunit of EC 4.2.1.20.
SYNONYMS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Trp synthase
Q5JDJ1, Q9YGB0
-
ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
TrpB1; gene trpB1, located adjacently to gene trpA in the trpCDEGFB1A operon
UniProt
Manually annotated by BRENDA team
TrpB2; gene trpB2, located outside the trpCDEGFB1A operon
UniProt
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
malfunction
-
the double-deletion mutant (DELTAtrpB1DELTAtrpB2) displays Trp auxotrophy, whereas individual single mutants (DELTAtrpB1 and DELTAtrpB2 strains) does not
metabolism
-
the last two steps of L-tryptophan (Trp) biosynthesis are catalyzed by Trp synthase, a heterotetramer composed of TrpA and TrpB. TrpB catalyzes the condensation of indole, synthesized by TrpA, and serine to Trp. TrpB2 catalyzes the TrpB reaction but does not interact with TrpA as in the case of TrpB1. TrpB1 and TrpB2 both contribute to Trp biosynthesis in Thermococcus kodakarensis and can utilize free indole, and indole salvage does not necessarily rely on TrpB2 to a greater extent
physiological function
-
TrpB2 acts as an indole rescue protein, which prevents the escape of this costly hydrophobic metabolite from the cell at the high growth temperatures of hyperthermophiles
physiological function
Q5JDJ1, Q9YGB0
trpB2 contributes in Trp biosynthesis
SUBSTRATE
PRODUCT                      
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
L-serine + indole
L-tryptophan + H2O
show the reaction diagram
-
-
-
-
?
L-serine + indole
L-tryptophan + H2O
show the reaction diagram
Q5JDJ1, Q9YGB0
-
-
-
?
additional information
?
-
-
TrpB2 does not bind to TrpA but is catalytically highly active, has an extremely low Km value for indole
-
-
-
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
L-serine + indole
L-tryptophan + H2O
show the reaction diagram
Q5JDJ1, Q9YGB0
-
-
-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
pyridoxal 5'-phosphate
Q5JDJ1, Q9YGB0
;
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.00077
indole
-
Km below 0.00077 mM, at 80C, pH not specified in the publication
0.0076
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB2, with TrpA
0.0081
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB2, without TrpA
0.035
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1 with TrpA
0.063
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1
50.2
L-serine
-
at 80C, pH not specified in the publication
additional information
additional information
Q5JDJ1, Q9YGB0
steady-state Michaelis-Menten kinetics, overview; steady-state Michaelis-Menten kinetics, overview
-
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.39
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB2, with or without TrpA
0.46
indole
-
at 80C, pH not specified in the publication
1.04
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1
3.46
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1 with TrpA
0.44
L-serine
-
at 80C, pH not specified in the publication
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.0006
indole
-
KCAT_KM below 0.0006 mM, at 80C, pH not specified in the publication
472
17
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1
472
48
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB2, without TrpA
472
51
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB2, with TrpA
472
99
indole
Q5JDJ1, Q9YGB0
pH 7.5, 85C, recombinant TrpB1 with TrpA
472
8700
L-serine
-
at 80C, pH not specified in the publication
95
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
7.5
Q5JDJ1, Q9YGB0
assay at; assay at
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
85
Q5JDJ1, Q9YGB0
assay at; assay at
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
61700
-
gel filtration
652353
92770
-
calculated from amino acid sequence
652353
98000
-
sedimentation equilibrium analysis
652353
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
heterotetramer
Q5JDJ1, Q9YGB0
Trp synthase is a heterotetramer composed of TrpA and TrpB, TrpA and TrpB1 assemble to form an alphabetabetaalpha heterotetramer
homodimer
-
2 * 46400, calculated from amino acid sequence
additional information
Q5JDJ1, Q9YGB0
complex formation of TrpB1 and TrpB2 with TrpA is analyzed by gel filtration
additional information
Q5JDJ1, Q9YGB0
complex formation of TrpB1 and TrpB2 with TrpA is analyzed by gel filtration, TrpA and TrpB2 do not form a complex
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
Mono Q column chromatography and Superdex 75 gel filtration
-
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
gene trpB1, phylogenetic tree, expression in Escherichia coli strain BL21, transcript levels of trpB1 in the host, DELTAtrpB1 strains by quantitative RT-PCR expression analysis; gene trpB2, phylogenetic tree, expression in Escherichia coli strain BL21, transcript levels of trpB2 in the host, DELTAtrpB2 strains by quantitative RT-PCR expression analysis
Q5JDJ1, Q9YGB0
expressed in Escherichia coli BL21(DE3) cells
-
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
transcript level of trpB1 (within the trp operon) increases by 110fold in Trp(-) medium compared to those in Trp(+) medium
Q5JDJ1, Q9YGB0
transcript level of trpB2 increases by 45fold in Trp(-) medium compared to those in Trp(+) medium
Q5JDJ1, Q9YGB0