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, Xu04c], 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].
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
Xu04c: 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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