This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Amino Acids Degradation → beta-Alanine Degradation|
Some taxa known to possess this pathway include : Rattus norvegicus
Expected Taxonomic Range: Mammalia
β-Alanine is a naturally occurring β-amino acid found in animals, plants [Stinson69] and microorganisms. It differs from L-alanine (an α-amino acid) in the position of the amino group on the β carbon, rather than the α carbon. In the pathway shown here, β-alanine is converted to malonate semialdehyde by transamination of α-ketoglutarate (2-oxoglutarate) to L-glutamate in an α-ketoglutarate-dependent reaction. Malonate semialdehyde is then converted to acetyl-CoA and CO2 by oxidative decarboxylation.
β-Alanine is synthesized in the liver, primarily by the degradation of uracil. Unlike L-alanine, β-alanine is not incorporated into proteins. In mammals, much of the cellular pool of β-alanine is incorporated into the dipeptide carnosine (β-alanyl-L-histidine). There is considerable research interest in the possible role of β-alanine and carnosine as neurotransmitters. The inhibitory neurotransmitter γ-aminobutyrate (GABA) is also a substrate for liver transaminases, as indicated in the EC 18.104.22.168 reaction. β-Alanine can also be transaminated by a pyruvate-dependent enzyme in liver [Kontani99]. These data and other aspects of mammalian β-amino acid metabolism and biochemistry are reviewed in [Griffith86].
Malonate-semialdehyde dehydrogenase from rat liver has been purified and characterized as the methylmalonate-semialdehyde dehydrogenase involved in valine degradation. The authors found it to be identical to the malonate-semialdehyde dehydrogenase involved in β-alanine degradation [Goodwin89]. They found that the production of acetyl-CoA in the presence of malonate semialdehyde, and propionyl-CoA in the presence of methylmalonate-semialdehyde, was stoichiometric with the amount of CoA added. No detectable malonyl-CoA or methylmalonyl-CoA was produced. The authors noted that this enzyme is unique among aldehyde dehydrogenases in its CoA dependency. They proposed that the formation of a CoA ester allows energy conservation during aldehyde oxidation [Harris93, Kedishvili92].
A microbial pathway for β-alanine degradation in Pseudomonas fluorescens is described in MetaCyc pathway β-alanine degradation II.
Variants: β-alanine degradation II
Relationship Links: KEGG:PART-OF:MAP00410
Carol A. Fulcher on Tue Aug 31, 2004:
An earlier version of this pathway included only reactions 2.6.1.- and 22.214.171.124. The pathway was updated by adding comments and enzymes for Rattus norvegicus. Reaction 2.6.1.- was replaced with reaction 126.96.36.199.
Fujimoto86: Fujimoto S, Mizutani N, Mizota C, Tamaki N (1986). "The level of beta-alanine aminotransferase activity in regenerating and differentiating rat liver." Biochim Biophys Acta 882(1);106-12. PMID: 3085724
Goodwin89: Goodwin GW, Rougraff PM, Davis EJ, Harris RA (1989). "Purification and characterization of methylmalonate-semialdehyde dehydrogenase from rat liver. Identity to malonate-semialdehyde dehydrogenase." J Biol Chem 264(25);14965-71. PMID: 2768248
Harris93: Harris RA, Popov KM, Kedishvili NY, Zhao Y, Shimomura Y, Robbins B, Crabb DW (1993). "Molecular cloning of the branched-chain alpha-keto acid dehydrogenase kinase and the CoA-dependent methylmalonate semialdehyde dehydrogenase." Adv Enzyme Regul 33;255-65. PMID: 8356911
Kedishvili92: Kedishvili NY, Popov KM, Rougraff PM, Zhao Y, Crabb DW, Harris RA (1992). "CoA-dependent methylmalonate-semialdehyde dehydrogenase, a unique member of the aldehyde dehydrogenase superfamily. cDNA cloning, evolutionary relationships, and tissue distribution." J Biol Chem 267(27);19724-9. PMID: 1527093
Kontani99: Kontani Y, Sakata SF, Matsuda K, Ohyama T, Sano K, Tamaki N (1999). "The mature size of rat 4-aminobutyrate aminotransferase is different in liver and brain." Eur J Biochem 264(1);218-22. PMID: 10447691
Anderson71: Anderson WA, Magasanik B (1971). "The pathway of myo-inositol degradation in Aerobacter aerogenes. Conversion of 2-deoxy-5-keto-D-gluconic acid to glycolytic intermediates." J Biol Chem 1971;246(18);5662-75. PMID: 4328832
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
StinesChaumeil06: Stines-Chaumeil C, Talfournier F, Branlant G (2006). "Mechanistic characterization of the MSDH (methylmalonate semialdehyde dehydrogenase) from Bacillus subtilis." Biochem J 395(1);107-15. PMID: 16332250
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