If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: superpathway of isoleucine biosynthesis
|Superclasses:||Biosynthesis → Amino Acids Biosynthesis → Proteinogenic Amino Acids Biosynthesis → L-isoleucine Biosynthesis|
Pathway Summary from MetaCyc:
L-isoleucine is almost always synthesized from 2-oxobutanoate. In the most common pathway, 2-oxobutanoate is generated from L-aspartate via L-threonine (this pathway). The key enzyme in this pathway is threonine deaminase, encoded by the ilvA gene.
In addition to the standard pathway, microorganisms have developed several alternative pathways for L-isoleucine biosynthesis. 2-oxobutanoate can be synthesized from L-glutamate via (2S, 3S)-3-methylaspartate (see L-isoleucine biosynthesis III) [Phillips72], from pyruvate (see L-isoleucine biosynthesis II) [Vollbrecht74, Charon74, Xu04], and by carboxylation of propanoate (see L-isoleucine biosynthesis IV) [Buchanan69, Sauer75, Eikmanns83]). In addition, there are several reports that some anaerobic bacteria can carboxylate 2-methylbutanoate to L-isoleucine via (S)-3-methyl-2-oxopentanoate (see L-isoleucine biosynthesis V) [Robinson69, Monticello84, Allison84].
Pathway Evidence Glyph:
This organism is in the expected taxonomic range for this pathway.
Key to pathway glyph edge colors:
An enzyme catalyzing this reaction is present in this organism
No enzyme catalyzing this reaction has been identified in this organism
The reaction is unique to this pathway in MetaCyc
Represents spontaneous reactions, or lines that do not represent reactions (e.g. in polymerization pathways)
Allison84: Allison MJ, Baetz AL, Wiegel J (1984). "Alternative pathways for biosynthesis of leucine and other amino acids in Bacteroides ruminicola and Bacteroides fragilis." Appl Environ Microbiol 48(6);1111-7. PMID: 6440485
Buchanan69: Buchanan BB (1969). "Role of ferredoxin in the synthesis of alpha-ketobutyrate from propionyl coenzyme A and carbon dioxide by enzymes from photosynthetic and nonphotosynthetic bacteria." J Biol Chem 244(15);4218-23. PMID: 5800441
Charon74: Charon NW, Johnson RC, Peterson D (1974). "Amino acid biosynthesis in the spirochete Leptospira: evidence for a novel pathway of isoleucine biosynthesis." J Bacteriol 117(1);203-11. PMID: 4808901
Xu04: Xu, H., Zhang, Y., Guo, X., Ren, S., Staempfli, A.A., Chiao, J., Jiang, W., Zhao, G. (2004). "Isoleucine biosynthesis in Leptospira interrogans serotype lai strain 56601 proceeds via a threonine-independent pathway." J. Bacteriol. 186(16):5400-5409. PMID: 15292141
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