If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
|Superclasses:||Degradation/Utilization/Assimilation → Carbohydrates Degradation|
Pathway Summary from MetaCyc:
Acetoin, along with diacetyl, is one of the compounds that give butter its characteristic flavor. It is natuarally found in many plants, including apples, asparagus, black currants, blackberry, wheat, broccoli, brussels sprouts, and cantaloupe. Many bacteria can grow on acetoin. Both aerobic bacteria, such as Bacillus subtilis [Huang99d], Ralstonia eutropha H16 [Priefert91] and Pseudomonas putida [Huang94], as well as anaerobes, such as Clostridium magnum [Kruger94] and Pelobacter carbinolicus DSM 2380 [Oppermann94], were shown to degrade acetoin by a direct cleavage to acetaldehyde and acetyl-CoA, catalyzed by the acetoin dehydrogenase complex.
The substrate range for growth of the strict anaerobe Pelobacter carbinolicus DSM 2380 is restricted to acetoin, methylacetoin, 2,3-butanediol, and ethylene glycol [Oppermann88]. During fermentation, acetoin is degraded to equimolar amounts of acetate and ethanol [Schink84]. The key enzyme in this degradation pathway is the acetoin dehydrogenase complex, a large enzyme complex that belongs to the 2-oxo acid dehydrogenase complex family, which also includes pyruvate dehydrogenase (PDHC), 2-oxoglutarate dehydrogenase complex, branched-chain α-keto acid dehydrogenase complex and glycine cleavage (GDHC).
The formation of the acetoin dehydrogenase complex is induced during growth on acetoin, and the induction was demonstrated in several related species, including Pelobacter venetianus, Pelobacter acetylenicus, Pelobacter propionicus, Acetobacterium carbinolicum, and Clostridium magnum [Oppermann94].
Pathway Evidence Glyph:
Key to pathway glyph edge colors:
An enzyme catalyzing this reaction is present in this organism
An enzyme catalyzing this reaction was identified in this organism by the Pathway Hole Filler
The reaction and any enzyme that catalyzes it (if one has been identified) is unique to this pathway
Blomqvist93: Blomqvist K, Nikkola M, Lehtovaara P, Suihko ML, Airaksinen U, Straby KB, Knowles JK, Penttila ME (1993). "Characterization of the genes of the 2,3-butanediol operons from Klebsiella terrigena and Enterobacter aerogenes." J Bacteriol 175(5);1392-404. PMID: 8444801
Huang99d: Huang M, Oppermann-Sanio FB, Steinbuchel A (1999). "Biochemical and molecular characterization of the Bacillus subtilis acetoin catabolic pathway." J Bacteriol 181(12);3837-41. PMID: 10368162
Kruger94: Kruger N, Oppermann FB, Lorenzl H, Steinbuchel A (1994). "Biochemical and molecular characterization of the Clostridium magnum acetoin dehydrogenase enzyme system." J Bacteriol 176(12);3614-30. PMID: 8206840
Oppermann88: Oppermann, F. B., Steinbuchel, A., Schlegel, H. G. (1988). "Utilization of methylacetoin by the strict anaerobe Pelobacter carbinolicus and consequences for the catabolism of acetoin." FEMS Microbiol. Lett. 55:47-52.
Oppermann94: Oppermann FB, Steinbuchel A (1994). "Identification and molecular characterization of the aco genes encoding the Pelobacter carbinolicus acetoin dehydrogenase enzyme system." J Bacteriol 176(2);469-85. PMID: 8110297
Priefert91: Priefert H, Hein S, Kruger N, Zeh K, Schmidt B, Steinbuchel A (1991). "Identification and molecular characterization of the Alcaligenes eutrophus H16 aco operon genes involved in acetoin catabolism." J Bacteriol 173(13);4056-71. PMID: 2061286
Schink84: Schink, B. (1984). "Fermentation of 2,3-butanediol by Pelobacter carbinolicus sp. nov. and Pelobacter propionicus sp. nov., and evidence for propionate formation from C2 compounds." Arch. Microbiol. 137:33-41.
Wardwell01: Wardwell SA, Yang YT, Chang HY, San KY, Rudolph FB, Bennett GN (2001). "Expression of the Klebsiella pneumoniae CG21 acetoin reductase gene in Clostridium acetobutylicum ATCC 824." J Ind Microbiol Biotechnol 27(4);220-7. PMID: 11687934
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