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Pathway Description
L-Alanine Metabolism
Escherichia coli (strain B / REL606)
Category:
Metabolite Pathway
Sub-Category:
Metabolic
Created: 2025-02-21
Last Updated: 2025-08-23
L-alanine is an essential component of proteins and peptidoglycan. The latter also contains about three molecules of D-alanine for every L-alanine. Only about 10 percent of the total alanine synthesized flows into peptidoglycan.There are at least 3 ways to begin the biosynthesis of alanine. The first method for alanine biosynthesis begins with L-cysteine produced from L-cysteine biosynthesis pathway. L-cysteine reacts with an [L-cysteine desulfurase] L-cysteine persulfide through a cysteine desulfurase resulting in a release of [L-cysteine desulfurase] l-cysteine persulfide and L-alanine. The second method starts with pyruvic acid reacting with L-glutamic acid through a glutamate-pyruvate aminotransferase resulting in a oxoglutaric acid and L-alanine. The third method starts with L-glutamic acid interacting with Alpha-ketoisovaleric acid through a valine transaminase resulting in an oxoglutaric acid and L-valine. L-valine reacts with pyruvic acid through a valine-pyruvate aminotransferase resulting Alpha-ketoisovaleric acid and L-alanine. This first step of the pathway, which can be catalyzed by either of two racemases (biosynthetic or catabolic), also serves an essential role in biosynthesis because its product, D-alanine, is an essential component of cell wall peptidoglycan (murein). D-alanine is metabolized by an ATP driven D-alanine ligase A and B resulting in D-alanyl-D-alanine. This product is incorporated into the peptidoglycan biosynthesis. L-alanine is metabolized with alanine racemase, either catabolic or metabolic resulting in a D-alanine. This compound reacts with water and a quinone through a D-amino acid dehydrogenase resulting in Pyruvic acid, hydroquinone and ammonium, thus entering the central metabolism and thereby can serve as a total source of carbon and energy. The role of the dadX racemase is degradative and dadX racemase can be induced by alanine and is subject to catabolite repression.
References
L-Alanine Metabolism References
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Pubmed: 9278503
Zawadzke LE, Bugg TD, Walsh CT: Existence of two D-alanine:D-alanine ligases in Escherichia coli: cloning and sequencing of the ddlA gene and purification and characterization of the DdlA and DdlB enzymes. Biochemistry. 1991 Feb 12;30(6):1673-82. doi: 10.1021/bi00220a033.
Pubmed: 1993184
Hayashi K, Morooka N, Yamamoto Y, Fujita K, Isono K, Choi S, Ohtsubo E, Baba T, Wanner BL, Mori H, Horiuchi T: Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110. Mol Syst Biol. 2006;2:2006.0007. doi: 10.1038/msb4100049. Epub 2006 Feb 21.
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Yamamoto Y, Aiba H, Baba T, Hayashi K, Inada T, Isono K, Itoh T, Kimura S, Kitagawa M, Makino K, Miki T, Mitsuhashi N, Mizobuchi K, Mori H, Nakade S, Nakamura Y, Nashimoto H, Oshima T, Oyama S, Saito N, Sampei G, Satoh Y, Sivasundaram S, Tagami H, Horiuchi T, et al.: Construction of a contiguous 874-kb sequence of the Escherichia coli -K12 genome corresponding to 50.0-68.8 min on the linkage map and analysis of its sequence features. DNA Res. 1997 Apr 28;4(2):91-113. doi: 10.1093/dnares/4.2.91.
Pubmed: 9205837
Liu L, Whalen W, Das A, Berg CM: Rapid sequencing of cloned DNA using a transposon for bidirectional priming: sequence of the Escherichia coli K-12 avtA gene. Nucleic Acids Res. 1987 Nov 25;15(22):9461-9. doi: 10.1093/nar/15.22.9461.
Pubmed: 2825136
Whalen WA, Berg CM: Gratuitous repression of avtA in Escherichia coli and Salmonella typhimurium. J Bacteriol. 1984 May;158(2):571-4.
Pubmed: 6373721
Sofia HJ, Burland V, Daniels DL, Plunkett G 3rd, Blattner FR: Analysis of the Escherichia coli genome. V. DNA sequence of the region from 76.0 to 81.5 minutes. Nucleic Acids Res. 1994 Jul 11;22(13):2576-86. doi: 10.1093/nar/22.13.2576.
Pubmed: 8041620
Kuramitsu S, Ogawa T, Ogawa H, Kagamiyama H: Branched-chain amino acid aminotransferase of Escherichia coli: nucleotide sequence of the ilvE gene and the deduced amino acid sequence. J Biochem. 1985 Apr;97(4):993-9. doi: 10.1093/oxfordjournals.jbchem.a135176.
Pubmed: 3897211
Lawther RP, Nichols B, Zurawski G, Hatfield GW: The nucleotide sequence preceding and including the beginning of the ilvE gene of the ilvGEDA operon of Escherichia coli K12. Nucleic Acids Res. 1979 Dec 20;7(8):2289-301. doi: 10.1093/nar/7.8.2289.
Pubmed: 392469
Lawther RP, Wek RC, Lopes JM, Pereira R, Taillon BE, Hatfield GW: The complete nucleotide sequence of the ilvGMEDA operon of Escherichia coli K-12. Nucleic Acids Res. 1987 Mar 11;15(5):2137-55. doi: 10.1093/nar/15.5.2137.
Pubmed: 3550695
Lobocka M, Hennig J, Wild J, Klopotowski T: Organization and expression of the Escherichia coli K-12 dad operon encoding the smaller subunit of D-amino acid dehydrogenase and the catabolic alanine racemase. J Bacteriol. 1994 Mar;176(5):1500-10. doi: 10.1128/jb.176.5.1500-1510.1994.
Pubmed: 7906689
Oshima T, Aiba H, Baba T, Fujita K, Hayashi K, Honjo A, Ikemoto K, Inada T, Itoh T, Kajihara M, Kanai K, Kashimoto K, Kimura S, Kitagawa M, Makino K, Masuda S, Miki T, Mizobuchi K, Mori H, Motomura K, Nakamura Y, Nashimoto H, Nishio Y, Saito N, Horiuchi T, et al.: A 718-kb DNA sequence of the Escherichia coli K-12 genome corresponding to the 12.7-28.0 min region on the linkage map. DNA Res. 1996 Jun 30;3(3):137-55. doi: 10.1093/dnares/3.3.137.
Pubmed: 8905232
Lauhon CT, Kambampati R: The iscS gene in Escherichia coli is required for the biosynthesis of 4-thiouridine, thiamin, and NAD. J Biol Chem. 2000 Jun 30;275(26):20096-103. doi: 10.1074/jbc.M002680200.
Pubmed: 10781607
This pathway was propagated using PathWhiz -
Pon, A. et al. Pathways with PathWhiz (2015) Nucleic Acids Res. 43(Web Server issue): W552–W559.
Propagated from SMP0000810
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