Escherichia coli K-12 substr. MG1655 Enzyme: transketolase I

Gene: tktA Accession Numbers: EG11427 (EcoCyc), b2935, ECK2930

Synonyms: tkt

Regulation Summary Diagram: ?

Regulation summary diagram for tktA

Subunit composition of transketolase I = [TktA]2
         transketolase I = TktA

Transketolase catalyzes the reversible transfer of a ketol group between several donor and acceptor substrates. This key enzyme is a reversible link between glycolysis and the pentose phosphate pathway. The enzyme is involved in the catabolism of pentose sugars, the formation of D-ribose 5-phosphate, and the provision of D-erythrose 4-phosphate, a precursor of aromatic amino acids and PLP [Josephson74, Sprenger95]. E. coli contains two transketolase isozymes, TktA and TktB. TktA is responsible for the major transketolase activity [Iida93].

In addition to its function in central carbon metabolism, transketolase appears to also have an unexpected role in chromosome structure [Hardy05].

Crystal structures of TktA in complex with donor and acceptor substrates have been solved, elucidating the reaction mechanism and mode of action of transketolase [Asztalos07]. The urea denaturation pathways of wild type and active site mutants of TktA has been investigated [Aucamp08, Dalby07], and the effects of temperature and pH on the structure, stability, aggregation and activity of transketolase have been determined [Jahromi11]. The acceptor specificity of TktA has been investigated [Yi12].

Transketolase mutants can not grow on pentoses [Josephson74, Josephson69]. Overproduction of TktB causes increased transketolase activity and suppresses the tktA mutant phenotype [Iida93]. A tktA tktB double mutant requires pyridoxine (or 4-hydroxy-L-threonine or glycolaldehyde), aromatic amino acids and vitamins for growth [Zhao94]. A tktA mutant affects chromosome topology [Hardy05].

Null mutations in tktA lead to metabolic flux alterations that increase intracellular levels of the growth inhibitory metabolite methylglyoxal, and thereby have an increased persistence phenotype [Girgis12].

Metabolic engineering for production of certain metabolites often involves transketolase; see [Patnaik94, Patnaik95, Flores96, Gosset96, Li99b, Li99c, Tatarko01, Chandran03, Yi03] and more.

TktA abundance is affected by the SOS inducer and mutagen 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000) [Touati96]. tktA is negatively regulated during entry into stationary phase. The effect by RpoS is likely indirect and might be mediated by an intermediate regulator that itself is directly regulated by RpoS [Jung05]. Expression of tktA and tktB is complementary, resulting in approximately constant levels of transketolase expression throughout growth [Rahman08].

Review: [Sprenger95b]

Please note that results reported in [Domain07] were later found to be erroneous; see corrigendum published in Molecular Microbiology, 80 (2011): 853. doi: 10.1111/j.1365-2958.2011.07642.x.

Citations: [Sprenger92, Hobbs96, French96, Chauhan96, Follstad98, Edwards00a, Sprenger93, Littlechild95, Hibbert07]

Locations: cytosol

Map Position: [3,077,666 <- 3,079,657] (66.33 centisomes, 239°)
Length: 1992 bp / 663 aa

Molecular Weight of Polypeptide: 72.212 kD (from nucleotide sequence), 73 kD (experimental) [Sprenger95 ]

Molecular Weight of Multimer: 145 kD (experimental) [Sprenger95]

Isozyme Sequence Similarity [Comment 1]:
transketolase II: YES

Unification Links: ASAP:ABE-0009625 , CGSC:103 , DIP:DIP-10998N , EchoBASE:EB1397 , EcoGene:EG11427 , EcoliWiki:b2935 , Mint:MINT-1260939 , ModBase:P27302 , OU-Microarray:b2935 , PortEco:tktA , PR:PRO_000024072 , Pride:P27302 , Protein Model Portal:P27302 , RefSeq:YP_026188 , RegulonDB:EG11427 , SMR:P27302 , String:511145.b2935 , UniProt:P27302

Relationship Links: InterPro:IN-FAMILY:IPR005474 , InterPro:IN-FAMILY:IPR005475 , InterPro:IN-FAMILY:IPR005476 , InterPro:IN-FAMILY:IPR005478 , InterPro:IN-FAMILY:IPR009014 , InterPro:IN-FAMILY:IPR020826 , InterPro:IN-FAMILY:IPR029061 , PDB:Structure:1QGD , PDB:Structure:2R5N , PDB:Structure:2R8O , PDB:Structure:2R8P , Pfam:IN-FAMILY:PF00456 , Pfam:IN-FAMILY:PF02779 , Pfam:IN-FAMILY:PF02780 , Prosite:IN-FAMILY:PS00801 , Prosite:IN-FAMILY:PS00802 , Smart:IN-FAMILY:SM00861

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Biological Process: GO:0009052 - pentose-phosphate shunt, non-oxidative branch Inferred from experiment [Josephson69, Josephson74]
GO:0008152 - metabolic process Inferred by computational analysis [GOA01a]
Molecular Function: GO:0004802 - transketolase activity Inferred from experiment Inferred by computational analysis [GOA01, GOA01a, Sprenger95]
GO:0030145 - manganese ion binding Inferred from experiment [Sprenger95]
GO:0030976 - thiamine pyrophosphate binding Inferred from experiment [Sprenger95]
GO:0042803 - protein homodimerization activity Inferred from experiment [Sprenger95]
GO:0003824 - catalytic activity Inferred by computational analysis [GOA01a]
GO:0016740 - transferase activity Inferred by computational analysis [UniProtGOA11a]
GO:0046872 - metal ion binding Inferred by computational analysis [UniProtGOA11a]
Cellular Component: GO:0005829 - cytosol Inferred from experiment Inferred by computational analysis [DiazMejia09, Ishihama08, LopezCampistrou05]

MultiFun Terms: metabolism carbon utilization carbon compounds
metabolism central intermediary metabolism non-oxidative branch, pentose pathway

Essentiality data for tktA knockouts: ?

Growth Medium Growth? T (°C) O2 pH Osm/L Growth Observations
LB Lennox Yes 37 Aerobic 7   Yes [Baba06, Comment 2]
M9 medium with 1% glycerol Yes 37 Aerobic 7.2 0.35 Yes [Joyce06, Comment 3]
MOPS medium with 0.4% glucose Yes 37 Aerobic 7.2 0.22 Yes [Baba06, Comment 2]
Yes [Feist07, Comment 4]

Last-Curated ? 04-Oct-2012 by Keseler I , SRI International

Enzymatic reaction of: transketolase

EC Number:

D-erythrose 4-phosphate + D-xylulose 5-phosphate <=> β-D-fructofuranose 6-phosphate + D-glyceraldehyde 3-phosphate

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.

In Pathways: pentose phosphate pathway , pentose phosphate pathway (non-oxidative branch)

Superoxide inhibits transketolase by oxidizing the 1,2-dihydroxyethyl thiamine pyrophosphate intermediate [Benov99].

Cofactors or Prosthetic Groups: thiamin diphosphate [Sprenger95], Mn2+ [Sprenger95]

Inhibitors (Irreversible): superoxide [Benov99]

Kinetic Parameters:

Km (μM)
β-D-fructofuranose 6-phosphate
D-glyceraldehyde 3-phosphate
D-erythrose 4-phosphate
D-xylulose 5-phosphate

T(opt): 20-40 °C [Sprenger95]

pH(opt): 8-8.5 [Sprenger95]

Enzymatic reaction of: transketolase

Synonyms: glycolaldehyde transferase, TK, sedoheptulose-7-phosphate:D-glyceraldehyde-3-phosphate glycoaldehydetransferase

EC Number:

D-sedoheptulose 7-phosphate + D-glyceraldehyde 3-phosphate <=> D-ribose 5-phosphate + D-xylulose 5-phosphate

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.

Alternative Substrates [Comment 5]:

In Pathways: pentose phosphate pathway , pentose phosphate pathway (non-oxidative branch)

Cofactors or Prosthetic Groups: thiamin diphosphate [Sprenger95], Mn2+ [Sprenger95], Mg2+ [Comment 6]

Inhibitors (Competitive): D-arabinose 5-phosphate [Sprenger95]

Inhibitors (Unknown Mechanism): 2'-methoxythiamin pyrophosphate [Reddick01]

Kinetic Parameters:

Km (μM)
D-glyceraldehyde 3-phosphate
D-ribose 5-phosphate
D-sedoheptulose 7-phosphate
D-xylulose 5-phosphate

T(opt): 20-40 °C [Sprenger95]

pH(opt): 8-8.5 [Sprenger95]

Sequence Features

Protein sequence of transketolase I with features indicated

Feature Class Location Attached Group Citations Comment
Amino-Acid-Sites-That-Bind 26  
UniProt: Substrate.
N6-acetyllysine-Modification 46  
[Zhang09, UniProt15]
UniProt: N6-acetyllysine.
Amino-Acid-Sites-That-Bind 66  
[Isupov99, UniProt12]
UniProt: Thiamine pyrophosphate.
Sequence-Conflict 103 -> 107  
[Sprenger93, UniProt10]
UniProt: (in Ref. 1; CAA48166);
Nucleotide-Phosphate-Binding-Region 114 -> 116 thiamin diphosphate
[Isupov99, UniProt14]
UniProt: Thiamine pyrophosphate.
Metal-Binding-Site 155  
UniProt: Magnesium.
Amino-Acid-Sites-That-Bind 156  
[Isupov99, UniProt12]
UniProt: Thiamine pyrophosphate; via amide nitrogen.
Metal-Binding-Site 185  
[Isupov99, UniProt12]
UniProt: Magnesium.
Metal-Binding-Site 187  
UniProt: Magnesium; via carbonyl oxygen.
Amino-Acid-Sites-That-Bind 261  
[Isupov99, UniProt12]
UniProt: Substrate.
Acetylation-Modification 347  
Amino-Acid-Sites-That-Bind 358  
UniProt: Substrate.
Amino-Acid-Sites-That-Bind 385  
UniProt: Substrate.
Active-Site 411  
UniProt: Proton donor; Non-Experimental Qualifier: probable.
Amino-Acid-Sites-That-Bind 437  
[Isupov99, UniProt12]
UniProt: Thiamine pyrophosphate.
Amino-Acid-Sites-That-Bind 461  
UniProt: Substrate.
Amino-Acid-Sites-That-Bind 469  
UniProt: Substrate.
Amino-Acid-Sites-That-Bind 473  
UniProt: Substrate.
Amino-Acid-Sites-That-Bind 520  
UniProt: Substrate.
Sequence-Conflict 584  
[Sprenger93, Blattner97, UniProt10]
UniProt: (in Ref. 1; CAA48166 and 3; AAA69102);

Gene Local Context (not to scale): ?

Gene local context diagram

Transcription Unit:

Transcription-unit diagram


10/20/97 Gene b2935 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG11427.


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Aucamp08: Aucamp JP, Martinez-Torres RJ, Hibbert EG, Dalby PA (2008). "A microplate-based evaluation of complex denaturation pathways: structural stability of Escherichia coli transketolase." Biotechnol Bioeng 99(6);1303-10. PMID: 17969139

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

Benov99: Benov L, Fridovich I (1999). "Why superoxide imposes an aromatic amino acid auxotrophy on Escherichia coli. The transketolase connection." J Biol Chem 274(7);4202-6. PMID: 9933617

Blattner97: Blattner FR, Plunkett G, Bloch CA, Perna NT, Burland V, Riley M, Collado-Vides J, Glasner JD, Rode CK, Mayhew GF, Gregor J, Davis NW, Kirkpatrick HA, Goeden MA, Rose DJ, Mau B, Shao Y (1997). "The complete genome sequence of Escherichia coli K-12." Science 277(5331);1453-74. PMID: 9278503

Chandran03: Chandran SS, Yi J, Draths KM, von Daeniken R, Weber W, Frost JW (2003). "Phosphoenolpyruvate availability and the biosynthesis of shikimic acid." Biotechnol Prog 19(3);808-14. PMID: 12790643

Chauhan96: Chauhan RP, Woodley JM, Powell LW (1996). "In situ product removal from E. coli transketolase-catalyzed biotransformations." Ann N Y Acad Sci 799;545-54. PMID: 8958111

Dalby07: Dalby PA, Aucamp JP, George R, Martinez-Torres RJ (2007). "Structural stability of an enzyme biocatalyst." Biochem Soc Trans 35(Pt 6);1606-9. PMID: 18031275

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

Domain07: Domain F, Bina XR, Levy SB (2007). "Transketolase A, an enzyme in central metabolism, derepresses the marRAB multiple antibiotic resistance operon of Escherichia coli by interaction with MarR." Mol Microbiol 66(2);383-94. PMID: 17850260

Edwards00a: Edwards JS, Palsson BO (2000). "Robustness analysis of the Escherichia coli metabolic network." Biotechnol Prog 16(6);927-39. PMID: 11101318

Feist07: Feist AM, Henry CS, Reed JL, Krummenacker M, Joyce AR, Karp PD, Broadbelt LJ, Hatzimanikatis V, Palsson BO (2007). "A genome-scale metabolic reconstruction for Escherichia coli K-12 MG1655 that accounts for 1260 ORFs and thermodynamic information." Mol Syst Biol 3;121. PMID: 17593909

Flores96: Flores N, Xiao J, Berry A, Bolivar F, Valle F (1996). "Pathway engineering for the production of aromatic compounds in Escherichia coli." Nat Biotechnol 14(5);620-3. PMID: 9630954

Follstad98: Follstad BD, Stephanopoulos G (1998). "Effect of reversible reactions on isotope label redistribution--analysis of the pentose phosphate pathway." Eur J Biochem 252(3);360-71. PMID: 9546650

French96: French C, Ward JM (1996). "Production and modification of E. coli transketolase for large-scale biocatalysis." Ann N Y Acad Sci 799;11-8. PMID: 8958067

Girgis12: Girgis HS, Harris K, Tavazoie S (2012). "Large mutational target size for rapid emergence of bacterial persistence." Proc Natl Acad Sci U S A 109(31);12740-5. PMID: 22802628

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."

Gosset96: Gosset G, Yong-Xiao J, Berry A (1996). "A direct comparison of approaches for increasing carbon flow to aromatic biosynthesis in Escherichia coli." J Ind Microbiol 17(1);47-52. PMID: 8987689

Hardy05: Hardy CD, Cozzarelli NR (2005). "A genetic selection for supercoiling mutants of Escherichia coli reveals proteins implicated in chromosome structure." Mol Microbiol 57(6);1636-52. PMID: 16135230

Hibbert07: Hibbert EG, Senussi T, Costelloe SJ, Lei W, Smith ME, Ward JM, Hailes HC, Dalby PA (2007). "Directed evolution of transketolase activity on non-phosphorylated substrates." J Biotechnol 131(4);425-32. PMID: 17825449

Hobbs96: Hobbs GR, Mitra RK, Chauhan RP, Woodley JM, Lilly MD (1996). "Enzyme-catalysed carbon-carbon bond formation: large-scale production of Escherichia coli transketolase." J Biotechnol 45(2);173-9. PMID: 9147449

Iida93: Iida A, Teshiba S, Mizobuchi K (1993). "Identification and characterization of the tktB gene encoding a second transketolase in Escherichia coli K-12." J Bacteriol 1993;175(17);5375-83. PMID: 8396116

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

Isupov99: Isupov M.N., Rupprecht M.P., Wilson K.S., Dauter Z., Littlechild J.A. (1999). "Crystal structure of Escherichia coli transketolase." Data submission to PDB data bank on 1999-04.

Jahromi11: Jahromi RR, Morris P, Martinez-Torres RJ, Dalby PA (2011). "Structural stability of E. coli transketolase to temperature and pH denaturation." J Biotechnol 155(2);209-16. PMID: 21723889

Josephson69: Josephson BL, Fraenkel DG (1969). "Transketolase mutants of Escherichia coli." J Bacteriol 100(3);1289-95. PMID: 4902809

Josephson74: Josephson BL, Fraenkel DG (1974). "Sugar metabolism in transketolase mutants of Escherichia coli." J Bacteriol 118(3);1082-9. PMID: 4597996

Joyce06: Joyce AR, Reed JL, White A, Edwards R, Osterman A, Baba T, Mori H, Lesely SA, Palsson BO, Agarwalla S (2006). "Experimental and computational assessment of conditionally essential genes in Escherichia coli." J Bacteriol 188(23);8259-71. PMID: 17012394

Jung05: Jung IL, Phyo KH, Kim IG (2005). "RpoS-mediated growth-dependent expression of the Escherichia coli tkt genes encoding transketolases isoenzymes." Curr Microbiol 50(6);314-8. PMID: 15968503

Li99b: Li K, Mikola MR, Draths KM, Worden RM, Frost JW (1999). "Fed-batch fermentor synthesis of 3-dehydroshikimic acid using recombinant Escherichia coli." Biotechnol Bioeng 64(1);61-73. PMID: 10397840

Li99c: Li K, Frost JW (1999). "Microbial synthesis of 3-dehydroshikimic acid: a comparative analysis of D-xylose, L-arabinose, and D-glucose carbon sources." Biotechnol Prog 15(5);876-83. PMID: 10514257

Littlechild95: Littlechild J, Turner N, Hobbs G, Lilly M, Rawas A, Watson H (1995). "Crystallization and preliminary X-ray crystallographic data with Escherichia coli transketolase." Acta Crystallogr D Biol Crystallogr 51(Pt 6);1074-6. PMID: 15299777

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

Patnaik94: Patnaik R, Liao JC (1994). "Engineering of Escherichia coli central metabolism for aromatic metabolite production with near theoretical yield." Appl Environ Microbiol 60(11);3903-8. PMID: 7993080

Patnaik95: Patnaik R, Spitzer RG, Liao JC (1995). "Pathway engineering for production of aromatics in Escherichia coli: Confirmation of stoichiometric analysis by independent modulation of AroG, TktA, and Pps activities." Biotechnol Bioeng 46(4);361-70. PMID: 18623323

Rahman08: Rahman M, Hasan MR, Shimizu K (2008). "Growth phase-dependent changes in the expression of global regulatory genes and associated metabolic pathways in Escherichia coli." Biotechnol Lett 30(5);853-60. PMID: 18175070

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Sprenger93: Sprenger GA (1993). "Nucleotide sequence of the Escherichia coli K-12 transketolase (tkt) gene." Biochim Biophys Acta 1216(2);307-10. PMID: 8241274

Sprenger95: Sprenger GA, Schorken U, Sprenger G, Sahm H (1995). "Transketolase A of Escherichia coli K12. Purification and properties of the enzyme from recombinant strains." Eur J Biochem 1995;230(2);525-32. PMID: 7607225

Sprenger95b: Sprenger GA (1995). "Genetics of pentose-phosphate pathway enzymes of Escherichia coli K-12." Arch Microbiol 1995;164(5);324-30. PMID: 8572885

Tatarko01: Tatarko M, Romeo T (2001). "Disruption of a global regulatory gene to enhance central carbon flux into phenylalanine biosynthesis in Escherichia coli." Curr Microbiol 43(1);26-32. PMID: 11375660

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UniProt10: UniProt Consortium (2010). "UniProt version 2010-11 released on 2010-11-02 00:00:00." Database.

UniProt12: UniProt Consortium (2012). "UniProt version 2012-09 released on 2012-09-12 00:00:00." Database.

UniProt14: UniProt Consortium (2014). "UniProt version 2014-01 released on 2014-01-01 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."

Yi03: Yi J, Draths KM, Li K, Frost JW (2003). "Altered glucose transport and shikimate pathway product yields in E. coli." Biotechnol Prog 19(5);1450-9. PMID: 14524706

Yi12: Yi D, Devamani T, Abdoul-Zabar J, Charmantray F, Helaine V, Hecquet L, Fessner WD (2012). "A pH-Based High-Throughput Assay for Transketolase: Fingerprinting of Substrate Tolerance and Quantitative Kinetics." Chembiochem 13(15);2290-300. PMID: 23001740

Yu08: Yu BJ, Kim JA, Moon JH, Ryu SE, Pan JG (2008). "The diversity of lysine-acetylated proteins in Escherichia coli." J Microbiol Biotechnol 18(9);1529-36. PMID: 18852508

Zhang09: Zhang J, Sprung R, Pei J, Tan X, Kim S, Zhu H, Liu CF, Grishin NV, Zhao Y (2009). "Lysine acetylation is a highly abundant and evolutionarily conserved modification in Escherichia coli." Mol Cell Proteomics 8(2);215-25. PMID: 18723842

Zhao94: Zhao G, Winkler ME (1994). "An Escherichia coli K-12 tktA tktB mutant deficient in transketolase activity requires pyridoxine (vitamin B6) as well as the aromatic amino acids and vitamins for growth." J Bacteriol 1994;176(19);6134-8. PMID: 7928977

Other References Related to Gene Regulation

MendozaVargas09: Mendoza-Vargas A, Olvera L, Olvera M, Grande R, Vega-Alvarado L, Taboada B, Jimenez-Jacinto V, Salgado H, Juarez K, Contreras-Moreira B, Huerta AM, Collado-Vides J, Morett E (2009). "Genome-wide identification of transcription start sites, promoters and transcription factor binding sites in E. coli." PLoS One 4(10);e7526. PMID: 19838305

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
Page generated by SRI International Pathway Tools version 19.0 on Fri Oct 9, 2015, biocyc12.