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 : Pseudomonas fluorescens
Expected Taxonomic Range: Proteobacteria
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 pyruvate to L-alanine, in a pyruvate-dependent reaction. α-Ketoglutarate (2-oxoglutarate) cannot be substituted for pyruvate [HAYAISHI61]. Malonate semialdehyde is then converted to acetyl-CoA and CO2 in an oxidative decarboxylation step. Both of the enzymes have been purified and characterized [HAYAISHI61] and their reactions have been established as the route of β-alanine degradation in this organism [HAYAISHI61]. These authors demonstrated stoichiometric quantities of malonate semialdehyde and L-alanine formed from β-alanine and pyruvate; and acetyl-CoA and CO2 formed from malonate semialdehyde and CoA.
In the malonate-semialdehyde dehydrogenase reaction, the authors noted that this enzyme simultaneously catalyzes the dehydrogenation and decarboxylation of malonate semialdehyde to a thioester CoA derivative. However, their data ruled out acetaldehyde and malonyl-CoA as free intermediates, as well as the participation of a malonyl semialdehyde-CoA intermediate [HAYAISHI61]. Therefore, intermediates in this reaction are hypothetical. The formation of CO2 was demonstrated using β-alanine-1-C14. Radioactive CO2 was formed from the carbonyl carbon of malonate semialdehyde [HAYAISHI61]. Using the same strain of P. fluorescens, β-alanine degradation was shown to be an inducible pathway when P. fluorescens was grown with β-alanine as a sole carbon and nitrogen source. The two reactions were identified as EC 126.96.36.199 and EC 188.8.131.52 [Hechtman70].
Unlike L-alanine, β-alanine is not incorporated into proteins. In microorganisms and plants, β-alanine is used in the biosynthesis of the vitamin pantothenate which is then used for coenzyme A and acyl carrier protein biosynthesis. Animals lack this pathway and must obtain the vitamin in their diet. In microorganisms, β-alanine is generally synthesized by decarboxylation of L-aspartate [Cronan80].
It should be noted that the strain of P. fluorescens in which this β-alanine degradation pathway was extensively studied [HAYAISHI61] has been classified as P. putida by the American Type Culture Collection (ATCC) under deposit number 11250.
A mammalian pathway for β-alanine degradation in rat liver is described in MetaCyc pathway β-alanine degradation I.
Variants: β-alanine degradation I
Relationship Links: KEGG:PART-OF:MAP00410
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
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
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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