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MetaCyc Enzyme: homoserine kinase

Gene: thrB Accession Numbers: EG10999 (MetaCyc), b0003, ECK0003

Species: Escherichia coli K-12 substr. MG1655

Subunit composition of homoserine kinase = [ThrB]2

Summary:
Homoserine kinase (ThrB) catalyzes the phosphorylation of homoserine to O-phospho-L-homoserine en route to generating threonine [Burr76, Shames84].

Though it is a substrate, homoserine can actually cause partial inhibition of the reaction at higher concentrations, with a Ki of ~2 mM [Shames84]. Substrate inhibition by high levels of ATP has also been observed [Chassagnole01]. ThrB has been subject to kinetic and mechanistic analysis [Shames84, Huo96]. The enzyme appears to have a second, regulatory binding site for L-homoserine [Shames84, Chassagnole01]. Site-directed mutagenesis has confirmed the role of Arg234 and the His residues H139 and H205 in substrate binding [Huo96a].

ThrB is required for growth of pdxB mutants on glucose and 3-hydroxyhomoserine or D-glycolaldehyde [Zhao96a]. Later, thrB was identified as a multicopy suppressor of the PLP auxotrophy of a pdxB deletion strain. ThrB was found to be part of a serendipitous metabolic pathway that produces an intermediate of the pyridoxal 5'-phosphate biosynthesis I pathway, 4-phospho-hydroxy-L-threonine, that lies downstream of PdxB [Kim10d]. The 4-hydroxy-L-threonine kinase activity of ThrB that is required for this pathway had already been identified in vitro [Shames84a]. The pathway diverts 3-phosphohydroxypyruvate from serine biosynthesis [Kim10d].

Translation of ThrA and ThrB is coupled [Little89].

Locations: cytosol

Map Position: [2,801 -> 3,733]

Molecular Weight of Polypeptide: 33.624 kD (from nucleotide sequence), 29 kD (experimental) [Burr76 ]

Molecular Weight of Multimer: 60.0 kD (experimental) [Burr76]

Unification Links: ASAP:ABE-0000010 , CGSC:110 , EchoBASE:EB0992 , EcoGene:EG10999 , EcoliWiki:b0003 , ModBase:P00547 , OU-Microarray:b0003 , PortEco:thrB , PR:PRO_000024067 , Pride:P00547 , Protein Model Portal:P00547 , RefSeq:NP_414544 , RegulonDB:EG10999 , SMR:P00547 , String:511145.b0003 , UniProt:P00547

Relationship Links: InterPro:IN-FAMILY:IPR000870 , InterPro:IN-FAMILY:IPR006203 , InterPro:IN-FAMILY:IPR006204 , InterPro:IN-FAMILY:IPR013750 , InterPro:IN-FAMILY:IPR014721 , InterPro:IN-FAMILY:IPR020568 , Pfam:IN-FAMILY:PF00288 , Pfam:IN-FAMILY:PF08544 , Prints:IN-FAMILY:PR00958 , Prosite:IN-FAMILY:PS00627

Gene-Reaction Schematic: ?

GO Terms:

Biological Process: GO:0009088 - threonine biosynthetic process Inferred from experiment Inferred by computational analysis [UniProtGOA12, UniProtGOA11, GOA06, Theze74, Theze74a]
GO:0006566 - threonine metabolic process Inferred by computational analysis [GOA01]
GO:0008652 - cellular amino acid biosynthetic process Inferred by computational analysis [UniProtGOA11]
GO:0016310 - phosphorylation Inferred by computational analysis [UniProtGOA11]
Molecular Function: GO:0004413 - homoserine kinase activity Inferred from experiment Inferred by computational analysis [GOA06, GOA01a, GOA01, Burr76]
GO:0000166 - nucleotide binding Inferred by computational analysis [UniProtGOA11]
GO:0005524 - ATP binding Inferred by computational analysis [UniProtGOA11, GOA06, GOA01]
GO:0016301 - kinase activity Inferred by computational analysis [UniProtGOA11]
GO:0016740 - transferase activity Inferred by computational analysis [UniProtGOA11]
Cellular Component: GO:0005829 - cytosol Inferred from experiment Inferred by computational analysis [DiazMejia09, Ishihama08, LopezCampistrou05]
GO:0005737 - cytoplasm Inferred by computational analysis [UniProtGOA11a, UniProtGOA11, GOA06]

MultiFun Terms: metabolism biosynthesis of building blocks amino acids threonine

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International


Enzymatic reaction of: homoserine kinase

Synonyms: ATP:L-homoserine O-phosphotransferase

EC Number: 2.7.1.39

L-homoserine + ATP <=> O-phospho-L-homoserine + ADP + H+

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. [Burr76]

Alternative Substrates for L-homoserine: L-aspartate-semialdehyde [Shames84 , Huo96a ]

In Pathways: isoleucine biosynthesis I , threonine biosynthesis , superpathway of lysine, threonine and methionine biosynthesis I , aspartate superpathway , threonine biosynthesis from homoserine

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International

Cofactors or Prosthetic Groups: K+ [Theze74b], Mg2+ [Burr76, Theze74b]

Cofactor Binding Comment: Mg facilitates binding of homoserine

Inhibitors (Competitive): 2-aminobutanoate [Theze74b, Burr76] , 2-chloro-L-alanine [Theze74b, Burr76] , L-cysteine [Theze74b, Burr76, Comment 1] , L-homocysteine [Theze74b, Burr76, Comment 1] , L-threonine [Theze74b, Burr76, Comment 1]

Inhibitors (Noncompetitive): L-lysine [Chassagnole01]

Inhibitors (Other): L-homoserine [Shames84]

Primary Physiological Regulators of Enzyme Activity: L-threonine

Kinetic Parameters:

Substrate
Km (μM)
Citations
L-homoserine
150.0
[Shames84]
ATP
200.0
[Shames84]

pH(opt): 7.8 [Theze74b]


Enzymatic reaction of: 4-hydroxythreonine kinase (homoserine kinase)

EC Number: 2.7.1.-

4-hydroxy-L-threonine + ATP <=> 4-phospho-hydroxy-L-threonine + ADP + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International

Kinetic Parameters:

Substrate
Km (μM)
Citations
4-hydroxy-L-threonine
2000.0
[Shames84a]


Sequence Features

Feature Class Location Citations Comment
Nucleotide-Phosphate-Binding-Region 91 -> 101
[UniProt10a]
UniProt: ATP; Non-Experimental Qualifier: potential;
Mutagenesis-Variant 139
[Huo96a, UniProt11]
Alternate sequence: L; UniProt: 35-fold decrease in kinase activity.
Mutagenesis-Variant 203
[Huo96a, UniProt11]
Alternate sequence: L; UniProt: 2-fold decrease in kinase activity but nearly no change in substrates affinity.
Mutagenesis-Variant 206
[Huo96a, UniProt11]
Alternate sequence: Q; UniProt: 3500-fold decrease in kinase activity.
Mutagenesis-Variant 235
[Huo96a, UniProt11]
Alternate sequence: L; UniProt: 26200-fold decrease in catalytic efficiency.
Alternate sequence: H; UniProt: 250-fold decrease in kinase activity but no change in substrates affinity.

History:
10/20/97 Gene b0003 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10999; confirmed by SwissProt match.


References

Burr76: Burr B, Walker J, Truffa-Bachi P, Cohen GN (1976). "Homoserine kinase from Escherichia coli K12." Eur J Biochem 1976;62(3);519-26. PMID: 177283

Chassagnole01: Chassagnole C, Rais B, Quentin E, Fell DA, Mazat JP (2001). "An integrated study of threonine-pathway enzyme kinetics in Escherichia coli." Biochem J 356(Pt 2);415-23. PMID: 11368768

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

GOA01: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

GOA01a: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA06: GOA, SIB (2006). "Electronic Gene Ontology annotations created by transferring manual GO annotations between orthologous microbial proteins."

Huo96: Huo X, Viola RE (1996). "Functional group characterization of homoserine kinase from Escherichia coli." Arch Biochem Biophys 330(2);373-9. PMID: 8660667

Huo96a: Huo X, Viola RE (1996). "Substrate specificity and identification of functional groups of homoserine kinase from Escherichia coli." Biochemistry 35(50);16180-5. PMID: 8973190

Ishihama08: Ishihama Y, Schmidt T, Rappsilber J, Mann M, Hartl FU, Kerner MJ, Frishman D (2008). "Protein abundance profiling of the Escherichia coli cytosol." BMC Genomics 9;102. PMID: 18304323

Kim10d: Kim J, Kershner JP, Novikov Y, Shoemaker RK, Copley SD (2010). "Three serendipitous pathways in E. coli can bypass a block in pyridoxal-5'-phosphate synthesis." Mol Syst Biol 6;436. PMID: 21119630

Little89: Little S, Hyde S, Campbell CJ, Lilley RJ, Robinson MK (1989). "Translational coupling in the threonine operon of Escherichia coli K-12." J Bacteriol 171(6);3518-22. PMID: 2542227

LopezCampistrou05: Lopez-Campistrous A, Semchuk P, Burke L, Palmer-Stone T, Brokx SJ, Broderick G, Bottorff D, Bolch S, Weiner JH, Ellison MJ (2005). "Localization, annotation, and comparison of the Escherichia coli K-12 proteome under two states of growth." Mol Cell Proteomics 4(8);1205-9. PMID: 15911532

Shames84: Shames SL, Wedler FC (1984). "Homoserine kinase of Escherichia coli: kinetic mechanism and inhibition by L-aspartate semialdehyde." Arch Biochem Biophys 235(2);359-70. PMID: 6097184

Shames84a: Shames SL, Ash DE, Wedler FC, Villafranca JJ (1984). "Interaction of aspartate and aspartate-derived antimetabolites with the enzymes of the threonine biosynthetic pathway of Escherichia coli." J Biol Chem 1984;259:15331-15339. PMID: 6150934

Theze74: Theze J, Saint-Girons I (1974). "Threonine locus of Escherichia coli K-12: genetic structure and evidence for an operon." J Bacteriol 118(3);990-8. PMID: 4364333

Theze74a: Theze J, Margarita D, Cohen GN, Borne F, Patte JC (1974). "Mapping of the structural genes of the three aspartokinases and of the two homoserine dehydrogenases of Escherichia coli K-12." J Bacteriol 117(1);133-43. PMID: 4148765

Theze74b: Theze J, Kleidman L, St Girons I (1974). "Homoserine kinase from Escherichia coli K-12: properties, inhibition by L-threonine, and regulation of biosynthesis." J Bacteriol 1974;118(2);577-81. PMID: 4364023

UniProt10a: UniProt Consortium (2010). "UniProt version 2010-07 released on 2010-06-15 00:00:00." Database.

UniProt11: UniProt Consortium (2011). "UniProt version 2011-06 released on 2011-06-30 00:00:00." Database.

UniProtGOA11: UniProt-GOA (2011). "Gene Ontology annotation based on manual assignment of UniProtKB keywords in UniProtKB/Swiss-Prot entries."

UniProtGOA11a: UniProt-GOA (2011). "Gene Ontology annotation based on the manual assignment of UniProtKB Subcellular Location terms in UniProtKB/Swiss-Prot entries."

UniProtGOA12: UniProt-GOA (2012). "Gene Ontology annotation based on UniPathway vocabulary mapping."

Zhao96a: Zhao G, Winkler ME (1996). "4-Phospho-hydroxy-L-threonine is an obligatory intermediate in pyridoxal 5'-phosphate coenzyme biosynthesis in Escherichia coli K-12." FEMS Microbiol Lett 1996;135(2-3);275-80. PMID: 8595869


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Sun Jan 25, 2015, biocyc12.