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Enzyme Nomenclature
Information on EC 4.3.1.19 - threonine ammonia-lyase
for references in articles please use BRENDA:EC4.3.1.19
Word Map on EC 4.3.1.19
- 4.3.1.19
- valine
-
biodegradative
-
branched-chain
- alpha-ketobutyrate
- l-isoleucine
- l-serine
- 2-ketobutyrate
-
acetohydroxy
-
isoleucine-valine
- homoserine
- acetolactate
- attenuata
- citramalate
-
feedback-resistant
- 2-oxobutyrate
-
acetohydroxyacid
-
sinoatrial
- molecular biology
- synthesis
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The enzyme appears in viruses and cellular organisms
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EC NUMBER 
COMMENTARY 
4.3.1.19
-
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RECOMMENDED NAME
GeneOntology No.
threonine ammonia-lyase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
2-aminobut-2-enoate = 2-iminobutanoate
(1b), spontaneous
-
-
-
2-iminobutanoate + H2O = 2-oxobutanoate + NH3
(1c), spontaneous
-
-
-
L-threonine = 2-aminobut-2-enoate + H2O
(1a)
-
-
-
L-threonine = 2-oxobutanoate + NH3
(overall reaction); that from P. putida is not. The enzyme from a number of sources also acts on L-serine, cf. EC 4.3.1.17, L-serine ammonia-lyase. The reaction catalysed probably involves initial elimination of water, hence the enzyme's original classification as EC 4.2.1.16, threonine dehydratase, followed by isomerization and hydrolysis of the product with C-N bond breakage; The enzyme from many sources is a pyridoxal-phosphate protein
-
-
-
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Deamination
-
-
-
-
elimination
elimination
-
-
alpha,beta-position of amino acid; beta-position of amino acid; of NH3, alpha,beta-position of amino acid
-
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
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SYSTEMATIC NAME
IUBMB Comments
L-threonine ammonia-lyase (2-oxobutanoate-forming)
Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme's original classification as EC 4.2.1.16, threonine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond [3,5]. The latter reaction, which can occur spontaneously, is also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase [5]. The enzymes from a number of sources also act on L-serine, cf. EC 4.3.1.17, L-serine ammonia-lyase.
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CAS REGISTRY NUMBER
COMMENTARY
9024-34-4
-
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
strain DL-1, ATCC 51573, gene GSU0486 or tcdB
UniProt
2 enzyme forms: an isoleucine-sensitive enzyme form and and an isoleucine-insensitive form
-
-
; 2 enzyme forms: an isoleucine-sensitive enzyme form and and an isoleucine-insensitive form
-
-
a genetically derepressed mutant strain of Escherichia coli K12; biosynthetic threonine deaminase; the enzyme exists in two distinct catalytically active species: a tetramer sensitive to L-Ile inhibition and a dimer insensitive to L-Ile inhibition
-
-
ilvA mutant encoding an enzyme that is resistant to feedback inhibition by L-Ile
-
-
; biodegradative threonine dehydratase
-
-
biodegradative threonine dehydratase
-
-
mutant with an activator site-deficient enzyme form
-
-
2 different forms: one enzyme form is sensitive to inhibition by Ile, the other form is insensitive to inhibition by Ile
-
-
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
malfunction
metabolism
physiological function
-
SP0454 contributes to virulence and colonization
malfunction
-
sp0454 deletion mutant is less virulent in a murine intranasal infection model
metabolism
-
involved in methionine metabolism, plays a predominant role in isoleucine synthesis
metabolism
-
involved in methionine metabolism, plays a predominant role in isoleucine synthesis
metabolism
-
involved in methionine metabolism, plays a predominant role in isoleucine synthesis
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
L-serine
pyruvate + NH3
-
dehydratase I: 26% of the activity with L-Thr, dehydratase II: 16% of the activity with L-Thr
-
-
?
L-serine
pyruvate + NH3
-
dehydratase I: 26% of the activity with L-Thr, dehydratase II: 16% of the activity with L-Thr
-
-
?
L-Thr
?
-
isoleucine-insensitive enzyme is subject to glucose-mediated catabolite repression
-
-
-
L-Thr
?
-
isoleucine-insensitive enzyme is subject to glucose-mediated catabolite repression
-
-
-
L-Thr
?
-
the enzyme is an important element in the flux control of Ile biosynthesis
-
-
-
L-Thr
?
-
increase of activity under gluconeogenic conditions in adult-rat hepatocytes cultured on collagen gel/nylon mesh
-
-
-
L-Thr
?
-
the enzyme is formed under anaerobic conditions, the enzyme is induced by L-Ser and L-Thr, cAMP is required for the synthesis of the enzyme
-
-
-
L-threonine
2-oxobutanoate + NH3
-
threonine deaminase is a key regulatory enzyme in the pathway for the biosynthesis of isoleucine, allosteric enzyme regulation model, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
a step in the pathway for the biosynthesis of isoleucine via isoleucine precursor 2-oxobutanoate generated from threonine, this pathway accounts for a minor fraction of isoleucine biosynthesis, while the majority of isoleucine is instead derived from acetyl-coenzyme A and pyruvate, possibly via the citramalate pathway, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
a step in the pathway for the biosynthesis of isoleucine via isoleucine precursor 2-oxobutanoate generated from threonine, this pathway accounts for a minor fraction of isoleucine biosynthesis, while the majority of isoleucine is instead derived from acetyl-coenzyme A and pyruvate, possibly via the citramalate pathway, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
-
biodegradation of L-threonine, the enzyme is involved in the biosynthetis pathway for isoleucine production, which is competitng with the valine biosynthetic pathway for the second precursor pyruvate
-
-
?
L-threonine
2-oxobutanoate + NH3
-
biodegradation of L-threonine, the enzyme is involved in the biosynthetis pathway for isoleucine production, which is competitng with the valine biosynthetic pathway for the second precursor pyruvate
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
?
additional information
?
-
-
GSU0486 also catalyzes the deamination of L-serine, EC 4.3.1.17
-
-
-
additional information
?
-
GSU0486 also catalyzes the deamination of L-serine, EC 4.3.1.17
-
-
-
additional information
?
-
GSU0486 also catalyzes the deamination of L-serine, EC 4.3.1.17
-
-
-
additional information
?
-
-
when pyridoxamine 5'-phosphate is incubated with the apoenzyme in the presence of small quantities of keto acids, e.g. pyruvate or 2-oxobutanoate, small amounts of L-Ala or L-aminobutanoate are formed, the reaction is not reversible
-
-
-
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
L-Thr
?
-
isoleucine-insensitive enzyme is subject to glucose-mediated catabolite repression
-
-
-
L-Thr
?
-
isoleucine-insensitive enzyme is subject to glucose-mediated catabolite repression
-
-
-
L-Thr
?
-
the enzyme is an important element in the flux control of Ile biosynthesis
-
-
-
L-Thr
?
-
increase of activity under gluconeogenic conditions in adult-rat hepatocytes cultured on collagen gel/nylon mesh
-
-
-
L-Thr
?
-
the enzyme is formed under anaerobic conditions, the enzyme is induced by L-Ser and L-Thr, cAMP is required for the synthesis of the enzyme
-
-
-
L-threonine
2-oxobutanoate + NH3
-
threonine deaminase is a key regulatory enzyme in the pathway for the biosynthesis of isoleucine, allosteric enzyme regulation model, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
Q74FW6
a step in the pathway for the biosynthesis of isoleucine via isoleucine precursor 2-oxobutanoate generated from threonine, this pathway accounts for a minor fraction of isoleucine biosynthesis, while the majority of isoleucine is instead derived from acetyl-coenzyme A and pyruvate, possibly via the citramalate pathway, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
Q74FW6
a step in the pathway for the biosynthesis of isoleucine via isoleucine precursor 2-oxobutanoate generated from threonine, this pathway accounts for a minor fraction of isoleucine biosynthesis, while the majority of isoleucine is instead derived from acetyl-coenzyme A and pyruvate, possibly via the citramalate pathway, overview
-
-
?
L-threonine
2-oxobutanoate + NH3
-
biodegradation of L-threonine, the enzyme is involved in the biosynthetis pathway for isoleucine production, which is competitng with the valine biosynthetic pathway for the second precursor pyruvate
-
-
?
L-threonine
2-oxobutanoate + NH3
-
biodegradation of L-threonine, the enzyme is involved in the biosynthetis pathway for isoleucine production, which is competitng with the valine biosynthetic pathway for the second precursor pyruvate
-
-
?
L-threonine
2-oxobutanoate + NH3
-
-
-
-
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
pyridoxamine 5'-phosphate
-
reactivates after dissociation of the coenzyme
pyridoxal 5'-phosphate
-
cofactor; contains 2 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
cofactor; contains 2 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
cofactor; contains 2 mol of pyridoxal 5'-phosphate per mol of enzyme; contains 4 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
contains 4 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
cofactor; contains 4 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
cofactor; contains 4 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
contains 2 mol of pyridoxal 5'-phosphate per mol of enzyme
pyridoxal 5'-phosphate
-
Km: 0.000682 mM; reactivates after dissociation of the coenzyme
pyridoxal 5'-phosphate
-
activates; reactivates after dissociation of the coenzyme
pyridoxal 5'-phosphate
-
cofactor; enzyme contains 1 mol of pyridoxal 5'-phosphate per 56000 Da subunit
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
K+
Li+
NH4+
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
2-oxobutanoate
-
20 mM, about 50% inhibition. Inhibition is not reversed by AMP
glyoxylate
-
20 mM, about 50% inhibition. Inhibition is not reversed by AMP
Ile
-
2 enzyme forms: an isoleucine-sensitive enzyme form and and isoleucine-insensitive form, pH-dependence of inhibition
Ile
-
native enzyme is totally inhibited by 15 mM Ile, the heterologous catabolic enzyme from E. coli retains 60% of its original activity even in presence of 200 mM Ile
Ile
-
competitive allosteric inhibitor, the enzyme exists in two distinct catalytically active species: a tetramer sensitive to L-Ile inhibition and a dimer insensitive to L-Ile inhibition
Ile
-
0.5 mM, wild type enzyme is completely inhibited at both pH 8.0 and pH 6.5, the mutant enzyme is sensitive only at pH 6.5. In contrast to the wild type enzyme 1 mM Val does not reverse L-Ile inhibition of the mutant enzyme
Ile
-
2 different forms: one enzyme form is sensitive to inhibition by Ile, the other form is insensitive to inhibition by Ile
Ile
-
feed-back inhibition; HgCl2 treated enzyme is less sensitive; L-Val partially reverses inhibition
isoleucine
-
activation below 0.01 mM, strong inhibition above, 50% inhibition at 0.064 mM, inhibition can be reversed by valine
isoleucine
-
allosteric effector inducing dimerization, inhibition is reversed by high concentrations of valine
isoleucine
-
end product inhibition, reversed by valine, the short C-terminal regulatory domain is composed of one ACT-like subdomain, which binds isoleucine and valine
L-isoleucine
-
at 1 mM the transgenic lines containing omr1-1, omr1-5, and omr1-8 have 85% activity, while the transgenic line containing omr1-7 has 70% activity, the wild-type has 20% activity
pyruvate
-
20 mM, about 50% inhibition. Inhibition is not reversed by AMP
pyruvate
-
uncompetitive inhibition and substrate inhibition with respect to L-Thr, noncompetitive inhibition with respect to AMP
pyruvate
-
noncompetitive inhibition with respect to L-Thr, mixed type inhibition with respect to AMP
additional information
-
feedback-inhibition of threonine deaminase by branched-chain amino acids
-
additional information
TcdB is not inhibited by isoleucine
-
additional information
-
feedback-inhibition of threonine deaminase by branched-chain amino acids
-
additional information
-
feedback-inhibition of threonine deaminase by branched-chain amino acids
-
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
isoleucine
-
activation below 0.01 mM, strong inhibition above, 50% inhibition at 0.064 mM
additional information
-
threonine aldolase mutations increase substrate availability for threonine deaminase
-
additional information
-
insensitive to the allosteric activation by AMP or CMP
-
additional information
the plant activates threonine deaminase in tissues attacked by herbivores
-
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
additional information
-
Monod-Wyman-Changeux symmetrical model analysis of steady-state kinetics for the wild-type and four mutant enzymes
-
16
L-threonine
-
in the presence of 5 mM AMP
32
L-threonine
-
in the presence of 5 mM CMP
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
additional information
-
activity is much lower in quail liver than in rat liver, regardless of the nutritional state. The specific activity in the normal rat liver is 15times higher than that of the control quail group. Activities in liver of the fastened, the 1% threonine-enriched and the 5% threonine-enriched group are about 2, 1.3 and 1.5times higher, respectively, than that of the control group of quails
additional information
-
activity is much higher in rat liver than in quail liver, regardless of the nutritional state. The specific activity in the normal rat liver is 15times higher than that of the control quail group. The specific activity in rat liver after fasting increases by a factor of 2.3 over that of normal fed state
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
7.5
8.5
8.8
8.9
9.2 - 9.6
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pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
7.5 - 9.5
8.5 - 11
-
pH 8.5: about 30% of maximal activity, pH 11.0: about 70% of maximal activity, with L-Thr as substrate
additional information
the enzyme is highly active in an alkaline pH range, little or no activity is observed at pH values below 6.0
7.5 - 9.5
-
pH 7.5: about 55% of maximal activity, pH 9.5: about 85% of maximal activity
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
22
37
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TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
45 - 80
-
45°C: about 25% of maximal activity, 80°C: about 35% of maximal activity
60 - 98
-
60°C: about 30% of maximal activity, 98°C: about 15% of maximal activity
additional information
active over a wide range of temperatures, optimal enzyme activity is observed at 58°C
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pI VALUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
additional information
-
isoleucine-sensitive enzyme form occurs predominantly in younger leaves, isoleucine-insensitive enzyme form occurs predominantly in older leaves
additional information
-
pH for growth is in the range of pH 6.0-pH 9.0, optimal growth around pH 7.0, optimal growth conditions, overview
additional information
-
pH for growth is in the range of pH 6.0-pH 9.0, optimal growth around pH 7.0, optimal growth conditions, overview
-
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
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PDB
SCOP
CATH
UNIPROT
ORGANISM
Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720);
Q5SLL4
Thermus thermophilus (strain HB8 / ATCC 27634 / DSM 579);
P11954
Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720);
P11954
Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720);
P11954
Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720);
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
32000
36000
45000
49800
-
4 * 49800, equilibrium sedimentation of the enzyme dialyzed against 6 M guanidine hydrochloride
53000
-
4 * 53000, the enzyme exists in two distinct catalytically active species: a tetramer sensitive to L-Ile inhibition and a dimer insensitive to L-Ile inhibition, SDS-PAGE
55000
59567
-
2 * 59567, mass spectrometry, addition of isoleucine induces dimerization, tetrmerization is restored by addition of high valine concentration; 4 * 59567, mass spectrometry
100000
-
determined by gel-filtration in the presence of CMP
120000
140000
-
native PAGE, in the presence of the allosteric effector isoleucine
190000
200000
210000
214000
-
meniscus depletion equilibrium sedimentation, analytical ultracentrifugation
45000
-
determined by gel-filtration in the absence of CMP and AMP
120000
-
determined by gel-filtration in the presence of AMP
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer
tetramer
additional information
-
the short C-terminal regulatory domain is composed of only one ACT-like subdomain
dimer
-
2 * 59567, mass spectrometry, addition of isoleucine induces dimerization, tetrmerization is restored by addition of high valine concentration
tetramer
-
4 * 53000, the enzyme exists in two distinct catalytically active species: a tetramer sensitive to L-Ile inhibition and a dimer insensitive to L-Ile inhibition, SDS-PAGE
tetramer
-
4 * 49800, equilibrium sedimentation of the enzyme dialyzed against 6 M guanidine hydrochloride
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
data for two crystal forms are collected to resolutions of 2.2 and 1.7 A, crystals obtainted in the presence of CMP diffract to a resolution of 3-3.5 A, in the presence of AMP poorly
-
two data sets of resolutions 2.2 A, crystal form I, and 1.7 A, crystal form II, are collected
-
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
0
-
10 h, 81% loss of activity in presence of 0.05 mM Ile, stable in presence of 1 mM Ile
27
-
10 h, 27% loss of activity in presence of 0.05 mM Ile, stable in presence of 1 mM Ile
37
-
10 min, 16% loss of activity of dehydratase I and 36% loss of activity of dehydratase II, loss of activity of dehydratase I is prevented by 1 mM Ile, but that of dehydratase II is not
43
45
-
15 min, complete loss of activity in absence of phosphate, 94% loss of activity in presence of 50 mM phosphate, 49% loss of activity in presence of 250 mM phosphate
47
55
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GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
dithiothreitol, allothreonine and pyridoxal phosphate are all required to maintain a stable form of threonine dehydratase
-
loss of activity of dehydratase I at 37 C is prevented by 1 mM Ile, but that of dehydratase II is not
-
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STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-20°C, 0.05 M potassium phosphate, pH 7.2, enzyme concentration 0.06 mg/ml, half-life: 4 weeks
-
0°C, rapid loss of activity unless maintained in presence of Ile and potassium phosphate
-
4°C, pH 7.2 or 9.0, 24 h, complete inactivation after 7 days, stable in presence of egg albumin
-
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
mutant strain DU-21 with an activator site-deficient enzyme form
-
partial
using a nickel-nitrilotriacetic acid affinity column
-
using a Sephadex G-25, a DEAE-cellulose DE52, a HiLoad26/60 Superdex 200 and a HiPrep 16/10 column
using Ni-NTA chromatography
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
a modified SlTD2 cDNA is cloned into the pET30a+ vector producing a truncated form of SlTD2 lacking the 51 amino acids corresponding to the N-terminal chloroplast-targeting sequence
expressed in Escherichia coli as a His-tagged fusion protein
expression in Brevibacterium flavum; expression in Corynebacterium glutamicum
-
gene tcdB, phylogenetic analysis of threonine ammonia-lyases
ilvA expression in Nicotiana tabaccum is effectively utilized as a selectable marker gene to identify tobacco transformants when coupled with L-O-methylthreonine as the selction agent
-
into the pRSETC vector for expression in Escherichia coli BL21DE3 pLysS cells
-
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
about 500 times higher transcript levels in flowers than in leaves or roots; induced transcription in response to osmotic stress
-
induced transcription in response to osmotic stress
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
E520A
-
omr1-7 allele, tolerates high concentrations of L-O-methylthreonine
H542L
-
omr1-8 allele, tolerates high concentrations of L-O-methylthreonine
R499C
-
omr1-5 allele, tolerates high concentrations of L-O-methylthreonine
R499C/R544H
-
omr1-1 allele, tolerates high concentrations of L-O-methylthreonine
Y449L
-
concentration of isoleucine needed to reach 50% inhibition increases by a factor 45, two different effector-binding sites are constituted in part by Y449 and Y543
Y543L
-
concentration of isoleucine needed to reach 50% inhibition increases by a factor 38, two different effector-binding sites are constituted in part by Y449 and Y543
G350A
-
site-directed mutagenesis, the affinity for both allosteric effectors is lower compared to the wild-type, valine binds exclusively to the R state, the mutation causes a shift in the equilibrium between the T and R conformational states of the protein toward the T state with L being higher than that of the wild-type enzyme
L352A
-
site-directed mutagenesis, the affinity for both allosteric effectors is lower compared to the wild-type, valine binds exclusively to the R state, the mutation causes a shift in the equilibrium between the T and R conformational states of the protein toward the T state with L being 6.5fold higher than that of the wild-type enzyme
N363A
-
site-directed mutagenesis, the mutant acts similar to the wild-type
Q347A
-
site-directed mutagenesis, mutant Q347A is very similar to the wild-type enzyme in most of its characteristics, except for a 1.5fold increase in L and a 5fold increase in KTIle
T367A
-
site-directed mutagenesis, the T367A mutation causes a decrease in the affinity of bsTD for both allosteric effectors and an increase in substrate affinity compared to the wild-type enzyme
Y371L
-
site-directed mutagenesis, the apparent affinities for both of the allosteric effectors are very low and the apparent dissociation constant for isoleucine from the T state is 50fold higher compared to the wild-type
Val323Ala
-
feedback inhibition by L-Ile is entirely abolished, so that the enzyme is always present in a relaxed high-activity state
E347F
-
mutation decreases the K0.5 values of Thr without significant change of the n(H) value compared to wild-type. Mutant is strongly feedback-resistant to Ile compared to the wild-type enzyme. IC50 (Ile) is increased compared to wild-type
E442A
-
mutation increases the K0.5 value of Thr and n(H) value, comparing to those of the wild-type enzyme. IC50 (Ile) is decreased compared to wild-type
F352A
-
mutation decreases the K0.5 values of Thr without significant change of the n(H) value compared to wild-type. Mutant is strongly feedback-resistant to Ile compared to the wild-type enzyme. IC50 (Ile) is increased compared to wild-type
F352A/I460F
-
double mutant is more resistant to Ile inhibition than any single site mutant. Double mutations retains more than 85% activity even at 10 mM Ile
F352A/R362F
-
mutant shows both higher activity and stronger resistance to Ile inhibition compared to wild-type mice. Overexpression of mutant in Escherichia coli JW3591 significantly increases the production of ketobutyrate and Ile in comparison to the reference strains overexpressing wild-type
G350E
-
mutation increases the K0.5 value of Thr and n(H) value, comparing to those of the wild-type enzyme. IC50 (Ile) is decreased compared to wild-type
G445E
-
mutation G445E increased the K0.5 value of Thr without change of n(H) value compared to wild-type. IC50 (Ile) is slightly increased compared to wild-type
I460F
-
mutation decreases the K0.5 values of Thr without significant change of the n(H) value compared to wild-type. Mutant is strongly feedback-resistant to Ile compared to the wild-type enzyme. IC50 (Ile) is increased compared to wild-type
I460F/R362F
-
double mutant is more resistant to Ile inhibition than any single site mutant. Double mutations retains more than 85% activity even at 10 mM Ile
R362F
-
mutation decreases the K0.5 values of Thr without significant change of the n(H) value compared to wild-type. Mutant is strongly feedback-resistant to Ile compared to the wild-type enzyme. IC50 (Ile) is increased compared to wild-type
Y369L
-
mutant shows an 91fold increased IC50 (Ile) value compared to wild-type
additional information
additional information
-
the enzyme from the regulatory mutant CU18 is indistinguishable from the wild type enzyme in molecular weight and subunit composition
additional information
-
mutants lacking yjgF generate an isoleucine-insensitive protein
additional information
-
mutant with an activator site-deficient enzyme form, the Km for L-Thr is increased 4fold as compared with the wild type enzyme
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
molecular biology
-
in contrast to the wild-type, all four transgenic TD lines are able to tolerate high concentrations of L-O-methylthreonine. This illustrates the potential use of these mutant omr genes as dominant selectable markers in plant transformation
synthesis
-
production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from a single unrelated carbon source via threonine biosynthesis in Escherichia coli, by overexpression of threonine deaminase, which is the key factor for providing propionyl-coenzyme A (propionyl-CoA), from different host bacteria, removal of the feedback inhibition of threonine by mutating and overexpressing the thrABC operon in Escherichia coli, and knock-out of the competitive pathways of catalytic conversion of propionyl-CoA to 3-hydroxyvaleryl-CoA. Construction of a series of strains and mutants leads to production of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer with differing monomer compositions in a modified M9 medium supplemented with 20 g/liter xylose. The largest 3-hydroxyvalerate fraction obtained in the copolymer is 17.5 mol%
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