|Gene:||ilvA||Accession Numbers: EG10493 (MetaCyc), b3772, ECK3764|
Synonyms: ile, threonine dehydratase
Species: Escherichia coli K-12 substr. MG1655
Subunit composition of threonine deaminase = [IlvA]4
Threonine deaminase (IlvA) carries out the first step in the synthesis of isoleucine. IlvA catalyzes the breakdown of L-threonine to generate 2-oxobutanoate and ammonia [Umbarger56, Umbarger57, Ramakrishnan64, Ramakrishnan65, Ramakrishnan65a]. Although the conversion of threonine into oxobutanoate is also the first step in the pathway of threonine degradation, IlvA is not thought to play a role in that pathway. This expectation is bolstered by the presence of an oxygen-responsive promoter for ilvA and the anaerobic nature of the degradation pathway.
Threonine deaminase is a tetramer [Grimminger73]. It has been alternately reported that either two or four pyridoxal phosphate molecules bind per tetramer [Koerner75, Eisenstein91]. In the complete absence of pyridoxal phosphate, the enzyme dissociates into nonfunctional 102 kD dimers [Calhoun73]. It has also been suggested that IlvA has several active multimeric forms, rather than being solely active as a tetramer [Kagan75]. The regulatory small molecules valine and isoleucine both bind threonine deaminase at four molecules per tetramer, the former cooperatively [Eisenstein94]. Isoleucine binds only twice per tetramer [Koerner75]. Crystal structures of threonine deaminase to 2.8 and 2.9 Å resolution reveal that it is a dimer of dimers, consisting of a set of carboxy-terminal regulatory domains projecting outward from a core of pyridoxal-containing amino-termini [Gallagher98a, Gallagher98b]. The regulatory domains possessed two effector-binding sites [Chen13d].
Valine and isoleucine work to promote states with high and low affinity, respectively, for threonine. Isoleucine also appears to directly impact catalysis [Eisenstein95].
IlvA abundance increases following treatment of cells with glycyl-leucine [Vonder72].
Mutations in ilvA code for enzymes with significantly reduced threonine deaminase activity, while overexpression of threonine demaminase resulted in growth inhibition most likely due to accumulation of toxic levels of α-ketobutyrate [Fisher93]. Inhibition of threonine demaminase is involved in homocysteine toxicity [Tuite05].
|Map Position: [3,953,354 -> 3,954,898]|
Molecular Weight of Polypeptide: 56.195 kD (from nucleotide sequence)
Unification Links: ASAP:ABE-0012321 , CGSC:609 , DIP:DIP-10018N , EchoBASE:EB0488 , EcoGene:EG10493 , EcoliWiki:b3772 , Mint:MINT-1305200 , ModBase:P04968 , OU-Microarray:b3772 , PortEco:ilvA , PR:PRO_000023001 , Pride:P04968 , Protein Model Portal:P04968 , RefSeq:NP_418220 , RegulonDB:EG10493 , SMR:P04968 , String:511145.b3772 , UniProt:P04968
Relationship Links: InterPro:IN-FAMILY:IPR000634 , InterPro:IN-FAMILY:IPR001721 , InterPro:IN-FAMILY:IPR001926 , InterPro:IN-FAMILY:IPR005787 , PDB:Structure:1TDJ , Pfam:IN-FAMILY:PF00291 , Pfam:IN-FAMILY:PF00585 , Prosite:IN-FAMILY:PS00165 , Prosite:IN-FAMILY:PS51672
|Biological Process:||GO:0006566 - threonine metabolic process
GO:0009082 - branched-chain amino acid biosynthetic process [UniProtGOA11a, Williams78]
GO:0009097 - isoleucine biosynthetic process [UniProtGOA12, UniProtGOA11a, GOA01a, Fisher93, Favre74, Calhoun73]
GO:0006520 - cellular amino acid metabolic process [GOA01a]
GO:0008152 - metabolic process [UniProtGOA11a]
GO:0008652 - cellular amino acid biosynthetic process [UniProtGOA11a]
|Molecular Function:||GO:0004794 - L-threonine ammonia-lyase activity
[GOA01, GOA01a, Fisher93, Favre74, Eisenstein91, Calhoun73]
GO:0016597 - amino acid binding [Eisenstein91]
GO:0030170 - pyridoxal phosphate binding [GOA01a, Eisenstein91]
GO:0003824 - catalytic activity [UniProtGOA11a]
GO:0016829 - lyase activity [UniProtGOA11a]
|Cellular Component:||GO:0005829 - cytosol [DiazMejia09]|
|MultiFun Terms:||metabolism → biosynthesis of building blocks → amino acids → isoleucine/valine|
Enzymatic reaction of: threonine deaminase
Synonyms: L-threonine hydro-lyase (deaminating), threonine dehydratase
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.
The reaction is irreversible in the direction shown.
Inhibition by cysteine is partially competitive with respect to threonine [Harris81].
pH(opt): 8-10 [Calhoun73]
|Protein-Segment||189 -> 192|
|Conserved-Region||339 -> 411|
|Conserved-Region||434 -> 504|
10/20/97 Gene b3772 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10493; confirmed by SwissProt match.
Chen13d: Chen L, Chen Z, Zheng P, Sun J, Zeng AP (2013). "Study and reengineering of the binding sites and allosteric regulation of biosynthetic threonine deaminase by isoleucine and valine in Escherichia coli." Appl Microbiol Biotechnol 97(7);2939-49. PMID: 22669632
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Eisenstein94: Eisenstein E, Yu HD, Schwarz FP (1994). "Cooperative binding of the feedback modifiers isoleucine and valine to biosynthetic threonine deaminase from Escherichia coli." J Biol Chem 269(47);29423-9. PMID: 7961922
Eisenstein95: Eisenstein E (1995). "Allosteric regulation of biosynthetic threonine deaminase from Escherichia coli: effects of isoleucine and valine on active-site ligand binding and catalysis." Arch Biochem Biophys 316(1);311-8. PMID: 7840631
Fisher93: Fisher KE, Eisenstein E (1993). "An efficient approach to identify ilvA mutations reveals an amino-terminal catalytic domain in biosynthetic threonine deaminase from Escherichia coli." J Bacteriol 175(20);6605-13. PMID: 8407838
Gallagher98a: Gallagher DT, Gilliland GL, Xiao G, Zondlo J, Fisher KE, Chinchilla D, Eisenstein E (1998). "Structure and control of pyridoxal phosphate dependent allosteric threonine deaminase." Structure 6(4);465-75. PMID: 9562556
Gallagher98b: Gallagher DT, Eisenstein E, Fisher KE, Zondlo J, Chinchilla D, Yu HD, Dill J, Winborne E, Ducote K, Xiao G, Gilliland GL (1998). "Polymorphous crystallization and diffraction of threonine deaminase from Escherichia coli." Acta Crystallogr D Biol Crystallogr 54(Pt 3);467-9. PMID: 9761930
Kagan75: Kagan ZS, Dorozhko AI, Kovaleva SV, Yakovleva LI (1975). "Studies of homogeneous "biosynthetic" L-threonine dehydratase from Escherichia coli K-12. Some kinetic properties and molecular multiplicity." Biochim Biophys Acta 403(1);208-20. PMID: 240428
Lawther87: Lawther RP, Wek RC, Lopes JM, Pereira R, Taillon BE, Hatfield GW (1987). "The complete nucleotide sequence of the ilvGMEDA operon of Escherichia coli K-12." Nucleic Acids Res 1987;15(5);2137-55. PMID: 3550695
Ramakrishnan64: Ramakrishnan T, Adelberg EA (1964). "Regulatory mechanisms in the biosynthesis of isoleucine and valine. I. Genetic derepression of enzyme formation." J Bacteriol 87;566-73. PMID: 14127571
Ramakrishnan65: Ramakrishnan T, Adelberg EA (1965). "Regulatory mechanisms in the biosynthesis of isoleucine and valine. II. Identification of two operator genes." J Bacteriol 89;654-60. PMID: 14273640
Ramakrishnan65a: Ramakrishnan T, Adelberg EA (1965). "Regulatory mechanisms in the biosynthesis of isoleucine and valine. 3. Map order of the structural genes and operator genes." J Bacteriol 89;661-4. PMID: 14273641
Squires81: Squires CH, Levinthal M, De Felice M (1981). "A role for threonine deaminase in the regulation of alpha-acetolactate biosynthesis in Escherichia coli K12." J Gen Microbiol 1981;127, pt 1;19-25. PMID: 7040602
Tuite05: Tuite NL, Fraser KR, O'byrne CP (2005). "Homocysteine toxicity in Escherichia coli is caused by a perturbation of branched-chain amino acid biosynthesis." J Bacteriol 187(13);4362-71. PMID: 15968045
Vonder72: Vonder Haar RA, Umbarger HE (1972). "Isoleucine and valine metabolism in Escherichia coli. XIX. Inhibition of isoleucine biosynthesis by glycyl-leucine." J Bacteriol 112(1);142-7. PMID: 4562390
Williams78: Williams AL, Whitfield SM, Williams LS (1978). "Synthesis and activities of branched-chain aminoacyl-tRNA synthetases in threonine deaminase mutants of Escherichia coli." J Bacteriol 134(1);92-9. PMID: 348689
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