If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
|Superclasses:||Degradation/Utilization/Assimilation → Amino Acids Degradation → Proteinogenic Amino Acids Degradation → L-threonine Degradation|
Two of the major routes for the degradation of L-threonine are known to occur both in mammals and in microorganisms. In the first route threonine is catabolized by catabolic threonine dehydratase (EC 18.104.22.168) to ammonia and 2-oxobutanoate, which is rapidly and irreversibly converted to propanoyl-CoA and formate (see L-threonine degradation I). A biosynthetic version of this enzyme has also been reported in certain anaerobic bacteria (see L-isoleucine biosynthesis I (from threonine)) [Umbarger57].
In the second route threonine is catabolized by EC 22.214.171.124, L-threonine 3-dehydrogenase to form L-2-amino-3-oxobutanoate, which is mainly cleaved by 2-amino-3-ketobutyrate CoA ligase, forming glycine and acetyl-CoA (see L-threonine degradation II). In the absence of the latter activity L-2-amino-3-oxobutanoate is spontaneously converted to aminoacetone, which is further metabolized into methylglyoxal (see L-threonine degradation III (to methylglyoxal)) or into (R)-1-amino-2-propanol O-2-phosphate, a precursor of vitamin B12 (see aminopropanol phosphate biosynthesis I).
A third route has been demonstrated in several bacteria and fungi. This route is based on the enzyme low-specificity L-threonine aldolase (EC 126.96.36.199), which cleaves threonine directly into glycine and acetaldehyde (see L-threonine degradation IV).
Unification Links: EcoCyc:THREOCAT-PWY
Boylan83: Boylan SA, Dekker EE (1983). "Growth, enzyme levels, and some metabolic properties of an Escherichia coli mutant grown on L-threonine as the sole carbon source." J Bacteriol 156(1);273-80. PMID: 6413491
Acebron09: Acebron SP, Martin I, del Castillo U, Moro F, Muga A (2009). "DnaK-mediated association of ClpB to protein aggregates. A bichaperone network at the aggregate surface." FEBS Lett 583(18);2991-6. PMID: 19698713
AlexanderCaudle90: Alexander-Caudle C, Latinwo LM, Jackson JH (1990). "Acetohydroxy acid synthase activity from a mutation at ilvF in Escherichia coli K-12." J Bacteriol 1990;172(6);3060-5. PMID: 2188950
Arifuzzaman06: Arifuzzaman M, Maeda M, Itoh A, Nishikata K, Takita C, Saito R, Ara T, Nakahigashi K, Huang HC, Hirai A, Tsuzuki K, Nakamura S, Altaf-Ul-Amin M, Oshima T, Baba T, Yamamoto N, Kawamura T, Ioka-Nakamichi T, Kitagawa M, Tomita M, Kanaya S, Wada C, Mori H (2006). "Large-scale identification of protein-protein interaction of Escherichia coli K-12." Genome Res 16(5);686-91. PMID: 16606699
Aristarkhov96: Aristarkhov A, Mikulskis A, Belasco JG, Lin EC (1996). "Translation of the adhE transcript to produce ethanol dehydrogenase requires RNase III cleavage in Escherichia coli." J Bacteriol 178(14);4327-32. PMID: 8763968
Avison01: Avison MB, Horton RE, Walsh TR, Bennett PM (2001). "Escherichia coli CreBC is a global regulator of gene expression that responds to growth in minimal media." J Biol Chem 276(29);26955-61. PMID: 11350954
Azakami94: Azakami H, Yamashita M, Roh JH, Suzuki H, Kumagai H, Murooka Y (1994). "Nucleotide sequence of the gene for monoamine oxidase (maoA) from Escherichia coli." Journal of Fermentation and Bioengineering 77(3):315-319.
Baba06: Baba T, Ara T, Hasegawa M, Takai Y, Okumura Y, Baba M, Datsenko KA, Tomita M, Wanner BL, Mori H (2006). "Construction of Escherichia coli K-12 in-frame, single-gene knockout mutants: the Keio collection." Mol Syst Biol 2;2006.0008. PMID: 16738554
Barak12: Barak Z, Chipman DM (2012). "Allosteric regulation in Acetohydroxyacid Synthases (AHASs)--different structures and kinetic behavior in isozymes in the same organisms." Arch Biochem Biophys 519(2);167-74. PMID: 22198286
Barak98: Barak R, Abouhamad WN, Eisenbach M (1998). "Both acetate kinase and acetyl coenzyme A synthetase are involved in acetate-stimulated change in the direction of flagellar rotation in Escherichia coli." J Bacteriol 1998;180(4);985-8. PMID: 9473056
Bashir06: Bashir Q, Rashid N, Akhtar M (2006). "Mechanism and substrate stereochemistry of 2-amino-3-oxobutyrate CoA ligase: implications for 5-aminolevulinate synthase and related enzymes." Chem Commun (Camb) (48);5065-7. PMID: 17146529
Becker02: Becker A, Kabsch W (2002). "X-ray structure of pyruvate formate-lyase in complex with pyruvate and CoA. How the enzyme uses the Cys-418 thiyl radical for pyruvate cleavage." J Biol Chem 277(42);40036-42. PMID: 12163496
Becker99a: Becker A, Fritz-Wolf K, Kabsch W, Knappe J, Schultz S, Volker Wagner AF (1999). "Structure and mechanism of the glycyl radical enzyme pyruvate formate-lyase." Nat Struct Biol 6(10);969-75. PMID: 10504733
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