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Escherichia coli K-12 substr. MG1655 Pathway: galactose degradation I (Leloir pathway)
Traceable author statement to experimental support

Pathway diagram: galactose degradation I (Leloir pathway)

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

Schematic showing all replicons, marked with selected genes

Genetic Regulation Schematic

Genetic regulation schematic for galactose degradation I (Leloir pathway)

Synonyms: Leloir pathway

Superclasses: BiosynthesisCarbohydrates BiosynthesisSugars BiosynthesisSugar Nucleotides Biosynthesis
Degradation/Utilization/AssimilationCarbohydrates DegradationSugars DegradationGalactose Degradation

The biological interconversion of galactose and glucose takes place only by way of the Leloir pathway (here named galactose degradation I (Leloir pathway)) and requires the three enzymes galactokinase , galactose-1-phosphate uridylyltransferase and UDP-glucose 4-epimerase.

The only biological importance of these enzymes appears to be to provide for the interconversion of galactosyl and glucosyl groups. galactose-1-epimerase also participates by producing the galactokinase substrate α-D-galactose from its β-anomer [Frey96]. The cycle requires an initial amount of UDP-D-glucose, which is produced by UTP--glucose-1-phosphate uridylyltransferase (EC [Neidhardt96]

Review: [Frey96]

Created 27-May-1998 by Pellegrini-Toole A, Marine Biological Laboratory


Frey96: Frey PA (1996). "The Leloir pathway: a mechanistic imperative for three enzymes to change the stereochemical configuration of a single carbon in galactose." FASEB J 10(4);461-70. PMID: 8647345

Lazarowski03: Lazarowski ER, Shea DA, Boucher RC, Harden TK (2003). "Release of cellular UDP-glucose as a potential extracellular signaling molecule." Mol Pharmacol 63(5);1190-7. PMID: 12695547

Neidhardt96: Neidhardt FC, Curtiss III R, Ingraham JL, Lin ECC, Low Jr KB, Magasanik B, Reznikoff WS, Riley M, Schaechter M, Umbarger HE "Escherichia coli and Salmonella, Cellular and Molecular Biology, Second Edition." American Society for Microbiology, Washington, D.C., 1996.

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Arabshahi86: Arabshahi A, Brody RS, Smallwood A, Tsai TC, Frey PA (1986). "Galactose-1-phosphate uridylyltransferase. Purification of the enzyme and stereochemical course of each step of the double-displacement mechanism." Biochemistry 25(19);5583-9. PMID: 3022797

Arabshahi88: Arabshahi A, Flentke GR, Frey PA (1988). "Uridine diphosphate galactose 4-epimerase. pH dependence of the reduction of NAD+ by a substrate analog." J Biol Chem 263(6);2638-43. PMID: 3277958

Barat01: Barat B, Bhattacharyya D (2001). "UDP-galactose 4-epimerase from Escherichia coli: formation of catalytic site during reversible folding." Arch Biochem Biophys 391(2);188-96. PMID: 11437350

Bauer91: Bauer AJ, Rayment I, Frey PA, Holden HM (1991). "The isolation, purification, and preliminary crystallographic characterization of UDP-galactose-4-epimerase from Escherichia coli." Proteins 9(2);135-42. PMID: 2008433

Bauer92: Bauer AJ, Rayment I, Frey PA, Holden HM (1992). "The molecular structure of UDP-galactose 4-epimerase from Escherichia coli determined at 2.5 A resolution." Proteins 12(4);372-81. PMID: 1579570

Beebe03: Beebe JA, Arabshahi A, Clifton JG, Ringe D, Petsko GA, Frey PA (2003). "Galactose mutarotase: pH dependence of enzymatic mutarotation." Biochemistry 42(15);4414-20. PMID: 12693937

Beebe98: Beebe JA, Frey PA (1998). "Galactose mutarotase: purification, characterization, and investigations of two important histidine residues." Biochemistry 37(42);14989-97. PMID: 9778377

Beisel11: Beisel CL, Storz G (2011). "The base-pairing RNA spot 42 participates in a multioutput feedforward loop to help enact catabolite repression in Escherichia coli." Mol Cell 41(3);286-97. PMID: 21292161

Beisel12: Beisel CL, Updegrove TB, Janson BJ, Storz G (2012). "Multiple factors dictate target selection by Hfq-binding small RNAs." EMBO J 31(8);1961-74. PMID: 22388518

Berger01: Berger E, Arabshahi A, Wei Y, Schilling JF, Frey PA (2001). "Acid-base catalysis by UDP-galactose 4-epimerase: correlations of kinetically measured acid dissociation constants with thermodynamic values for tyrosine 149." Biochemistry 40(22);6699-705. PMID: 11380265

Bhattacharyya99: Bhattacharyya U, Dhar G, Bhaduri A (1999). "An arginine residue is essential for stretching and binding of the substrate on UDP-glucose-4-epimerase from Escherichia coli. Use of a stacked and quenched uridine nucleotide fluorophore as probe." J Biol Chem 274(21);14573-8. PMID: 10329648

Bingham87: Bingham AH, Busby SJ (1987). "Translation of galE and coordination of galactose operon expression in Escherichia coli: effects of insertions and deletions in the non-translated leader sequence." Mol Microbiol 1(1);117-24. PMID: 2838723

Blackburn76: Blackburn P, Ferdinand W (1976). "The concerted inactivation of Escherichia coli uridine diphosphate galactose 4-epimerase by sugar nucleotide together with a free sugar." Biochem J 155(2);225-9. PMID: 779771

Bork93: Bork P, Sander C, Valencia A (1993). "Convergent evolution of similar enzymatic function on different protein folds: the hexokinase, ribokinase, and galactokinase families of sugar kinases." Protein Sci 2(1);31-40. PMID: 8382990

Bouffard94: Bouffard GG, Rudd KE, Adhya SL (1994). "Dependence of lactose metabolism upon mutarotase encoded in the gal operon in Escherichia coli." J Mol Biol 1994;244(3);269-78. PMID: 7966338

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

Burke93: Burke JR, Frey PA (1993). "The importance of binding energy in catalysis of hydride transfer by UDP-galactose 4-epimerase: a 13C and 15N NMR and kinetic study." Biochemistry 1993;32(48);13220-30. PMID: 8241177

Debouck85: Debouck C, Riccio A, Schumperli D, McKenney K, Jeffers J, Hughes C, Rosenberg M, Heusterspreute M, Brunel F, Davison J (1985). "Structure of the galactokinase gene of Escherichia coli, the last (?) gene of the gal operon." Nucleic Acids Res 13(6);1841-53. PMID: 3158881

Deeley75: Deeley R, Blackburn P, Ferdinand W (1975). "The first enzyme of the gal operon in inducible and operator-constitutive strains of Escherichia coli. A comparison of the porperties and amino-terminal sequences of UDP galactose 4-epimerase." Eur J Biochem 60(2);371-7. PMID: 1107041

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

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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