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MetaCyc Enzyme: 2-amino-3-ketobutyrate CoA ligase

Gene: kbl Accession Numbers: EG10512 (MetaCyc), b3617, ECK3607

Species: Escherichia coli K-12 substr. MG1655

Subunit composition of 2-amino-3-ketobutyrate CoA ligase = [Kbl]2

2-Amino-3-ketobutyrate CoA ligase (Kbl, AKB ligase) catalyzes the reversible, coenzyme A-dependent cleavage/condensation reaction between 2-amino-3-oxobutanoate (2-amino-3-ketobutyrate) and glycine plus acetyl-CoA. It is the second reaction in the threonine dehydrogenase-initiated pathway by which threonine is converted to glycine which is then converted to serine. This pathway is the primary route for threonine utilization in prokaryotes and is an alternate pathway for serine biosynthesis in E. coli [Mukherjee87, Ravnikar87]. Because 2-amino-3-oxobutanoate can spontaneously decarboxylate to aminoacetone, a second threonine dehydrogenase-initiated pathway is also possible (see L-threonine degradation III (to methylglyoxal)).

The crystal structure of Kbl in complex with a pyridoxal-5'-phosphate-substrate intermediate has been determined at 2.0 Å resolution and a reaction mechanism was proposed. Kbl belongs to the α family of PLP-dependent enzymes. It was noted that this enzyme has been evolutionarily conserved and E. coli Kbl shares 54% amino acid sequence identity with the human enzyme [Schmidt01]. Details of the condensation mechanism have been studied [Bashir06].

Review: Reitzer, L. (2005) "Catabolism of Amino Acids and Related Compounds" EcoSal 3.4.7 [ECOSAL]

Gene Citations: [Aronson88, Rex91]

Locations: cytosol

Map Position: [3,789,378 <- 3,790,574]

Molecular Weight of Polypeptide: 43.117 kD (from nucleotide sequence), 42.0 kD (experimental) [Mukherjee87 ]

Molecular Weight of Multimer: 85.0 kD (experimental) [Mukherjee87]

pI: 5.99

Unification Links: ASAP:ABE-0011832 , CGSC:18205 , DIP:DIP-48030N , EchoBASE:EB0507 , EcoGene:EG10512 , EcoliWiki:b3617 , Mint:MINT-1315923 , ModBase:P0AB77 , OU-Microarray:b3617 , PortEco:kbl , PR:PRO_000023046 , Pride:P0AB77 , Protein Model Portal:P0AB77 , RefSeq:NP_418074 , RegulonDB:EG10512 , SMR:P0AB77 , String:511145.b3617 , UniProt:P0AB77

Relationship Links: InterPro:IN-FAMILY:IPR001917 , InterPro:IN-FAMILY:IPR004839 , InterPro:IN-FAMILY:IPR011282 , InterPro:IN-FAMILY:IPR015421 , InterPro:IN-FAMILY:IPR015422 , InterPro:IN-FAMILY:IPR015424 , PDB:Structure:1FC4 , Pfam:IN-FAMILY:PF00155 , Prosite:IN-FAMILY:PS00599

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Biological Process: GO:0006567 - threonine catabolic process Inferred by computational analysis [GOA01a]
GO:0008152 - metabolic process Inferred by computational analysis [GOA01a]
GO:0009058 - biosynthetic process Inferred by computational analysis [GOA01a]
GO:0019518 - L-threonine catabolic process to glycine Inferred by computational analysis [UniProtGOA12, GOA06]
Molecular Function: GO:0016874 - ligase activity Inferred from experiment [Mukherjee87]
GO:0030170 - pyridoxal phosphate binding Inferred from experiment Inferred by computational analysis [GOA06, GOA01a, Mukherjee87, Schmidt01]
GO:0042803 - protein homodimerization activity Inferred from experiment [Mukherjee87]
GO:0046872 - metal ion binding Inferred from experiment [Mukherjee87]
GO:0003824 - catalytic activity Inferred by computational analysis [GOA01a]
GO:0008890 - glycine C-acetyltransferase activity Inferred by computational analysis [GOA06, GOA01, GOA01a]
GO:0016740 - transferase activity Inferred by computational analysis [UniProtGOA11a, GOA01a]
GO:0016746 - transferase activity, transferring acyl groups Inferred by computational analysis [UniProtGOA11a]
Cellular Component: GO:0005737 - cytoplasm Inferred from experiment [Schmidt01]
GO:0005829 - cytosol Inferred from experiment Inferred by computational analysis [DiazMejia09, Ishihama08, LopezCampistrou05]

MultiFun Terms: metabolism carbon utilization amino acids
metabolism central intermediary metabolism threonine catabolism

Imported from EcoCyc 02-Jun-2015 by Paley S , SRI International

Enzymatic reaction of: 2-amino-3-ketobutyrate CoA ligase

Synonyms: glycine C-acetyltransferase, AKB ligase, aminoacetone synthase, aminoacetone synthetase, acetyl-CoA:glycine C-acetyltransferase

EC Number:

glycine + acetyl-CoA <=> 2-amino-3-oxobutanoate + coenzyme A

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

This reaction is reversible. [Mukherjee87]

Alternative Substrates for acetyl-CoA [Comment 1 ]: butanoyl-CoA [Mukherjee87 ] , propanoyl-CoA [Mukherjee87 ]

In Pathways: superpathway of L-threonine metabolism , L-threonine degradation II

Imported from EcoCyc 02-Jun-2015 by Paley S , SRI International

The enzyme activity was assayed in the reverse direction as the amount of coenzyme A released by the condensation of acetyl-CoA with glycine. No activity was seen with valeryl-CoA, succinyl-CoA, or glutaryl-CoA. The enzyme was specific for glycine and no activity was seen with glycinamide, glycine methylester, 2-aminoethanol, aminomethylphosphonic acid, aminomalonate, L-alanine, L-serine, L-threonine, L-valine, or L-leucine. Varying degrees of inhibition were seen with the divalent cations Mn2+, Ni2+ Ca2+ Sr2+ Ba2+ Zn2+ Hg2+ Cu2+ and Cd2+, with the latter three showing strongest inhibition [Mukherjee87].

The enzyme was also shown to have L-threonine aldolase activity, cleaving L-threonine to acetaldehyde and glycine. Although the Km for glycine (ligase activity) was 10 mM and the Km for L-threonine (aldolase activity) was 0.9 mM, the Vmax values were 2.5 μmol of CoA released/min per mg for the ligase activity versus 0.014 μmol of acetaldehyde formed (NADH oxidized)/min per mg for the aldolase activity [Marcus93].

Cofactors or Prosthetic Groups: pyridoxal 5'-phosphate [Comment 2]

Inhibitors (Competitive): aminomalonate [Comment 3]

Inhibitors (Unknown Mechanism): diacetyl [Mukherjee92] , cyclohexane-1,2-dione [Mukherjee92] , phenylglyoxal [Mukherjee92] , 4-(oxoacetyl)phenoxyacetate [Mukherjee92] , Hg2+ [Mukherjee87] , Cu2+ [Mukherjee87] , Cd2+ [Mukherjee87] , L-cysteine [Mukherjee87] , L-dithiothreitol [Mukherjee87] , glutathione [Mukherjee87] , aminomethylphosphonate [Mukherjee87] , coenzyme A [Comment 4]

Primary Physiological Regulators of Enzyme Activity: L-cysteine , glutathione , coenzyme A , aminomalonate

Kinetic Parameters:

Km (μM)
[Mukherjee87, BRENDA14]

pH(opt): 7.5 [BRENDA14, Mukherjee87]

Sequence Features

Feature Class Location Citations Comment
Sequence-Conflict 43
[Aronson88, UniProt10a]
UniProt: (in Ref. 1; CAA29883);
Protein-Segment 111 -> 112
UniProt: Pyridoxal phosphate binding; Sequence Annotation Type: region of interest;
Amino-Acid-Sites-That-Bind 136
[Schmidt01, UniProt15]
UniProt: Substrate.
Sequence-Conflict 171
[Aronson88, UniProt10a]
UniProt: (in Ref. 1; CAA29883);
Sequence-Conflict 183
[Aronson88, UniProt10a]
UniProt: (in Ref. 1; CAA29883);
Amino-Acid-Sites-That-Bind 185
[Schmidt01, UniProt15]
UniProt: Pyridoxal phosphate.
Protein-Segment 210 -> 213
UniProt: Pyridoxal phosphate binding; Sequence Annotation Type: region of interest;
Protein-Segment 241 -> 244
UniProt: Pyridoxal phosphate binding; Sequence Annotation Type: region of interest;
N6-pyridoxal-phosphate-Lys-Modification 244
UniProt: N6-(pyridoxal phosphate)lysine.
Protein-Segment 274 -> 275
UniProt: Pyridoxal phosphate binding; Sequence Annotation Type: region of interest;
Amino-Acid-Sites-That-Bind 368
[Schmidt01, UniProt15]
UniProt: Substrate.

10/20/97 Gene b3617 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10512.


Aronson88: Aronson BD, Ravnikar PD, Somerville RL (1988). "Nucleotide sequence of the 2-amino-3-ketobutyrate coenzyme A ligase (kbl) gene of E. coli." Nucleic Acids Res 16(8);3586. PMID: 3287333

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

BRENDA14: BRENDA team (2014). "Imported from BRENDA version existing on Aug 2014."

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

ECOSAL: EcoSal "Escherichia coli and Salmonella: Cellular and Molecular Biology." Online edition.

GOA01: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA01a: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

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

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

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

Marcus93: Marcus JP, Dekker EE (1993). "Identity and some properties of the L-threonine aldolase activity manifested by pure 2-amino-3-ketobutyrate ligase of Escherichia coli." Biochim Biophys Acta 1164(3);299-304. PMID: 8343529

Mukherjee87: Mukherjee JJ, Dekker EE (1987). "Purification, properties, and N-terminal amino acid sequence of homogeneous Escherichia coli 2-amino-3-ketobutyrate CoA ligase, a pyridoxal phosphate-dependent enzyme." J Biol Chem 1987;262(30);14441-7. PMID: 3117785

Mukherjee90: Mukherjee JJ, Dekker EE (1990). "2-Amino-3-ketobutyrate CoA ligase of Escherichia coli: stoichiometry of pyridoxal phosphate binding and location of the pyridoxyllysine peptide in the primary structure of the enzyme." Biochim Biophys Acta 1990;1037(1);24-9. PMID: 2104756

Mukherjee92: Mukherjee JJ, Dekker EE (1992). "Inactivation of Escherichia coli 2-amino-3-ketobutyrate CoA ligase by phenylglyoxal and identification of an active-site arginine peptide." Arch Biochem Biophys 299(1);147-53. PMID: 1444446

Ravnikar87: Ravnikar PD, Somerville RL (1987). "Genetic characterization of a highly efficient alternate pathway of serine biosynthesis in Escherichia coli." J Bacteriol 169(6);2611-7. PMID: 3108237

Rex91: Rex JH, Aronson BD, Somerville RL (1991). "The tdh and serA operons of Escherichia coli: mutational analysis of the regulatory elements of leucine-responsive genes." J Bacteriol 173(19);5944-53. PMID: 1917830

Schmidt01: Schmidt A, Sivaraman J, Li Y, Larocque R, Barbosa JA, Smith C, Matte A, Schrag JD, Cygler M (2001). "Three-dimensional structure of 2-amino-3-ketobutyrate CoA ligase from Escherichia coli complexed with a PLP-substrate intermediate: inferred reaction mechanism." Biochemistry 40(17);5151-60. PMID: 11318637

UniProt10: UniProt Consortium (2010). "UniProt version 2010-07 released on 2010-06-15 00:00:00." Database.

UniProt10a: UniProt Consortium (2010). "UniProt version 2010-11 released on 2010-11-02 00:00:00." Database.

UniProt15: UniProt Consortium (2015). "UniProt version 2015-01 released on 2015-01-16 00:00:00." Database.

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

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

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 19.0 on Wed Sep 2, 2015, BIOCYC14B.