ilvA, ilvI, ilvH, ilvC, ilvD, ilvE
Overview: Isoleucine biosynthesis in GapMind is based on MetaCyc pathways L-isoleucine biosynthesis I (from threonine) (link), II via citramalate (link), or IV from propanoate (link). These pathways share a common intermediate, 2-oxobutanoate, but vary in how the 2-oxobutanoate is formed. Pathway IV is included because propanoate is a common fermentative end product and need not be a nutrient requirement, but it is not always clear if it could be the main pathway to isoleucine. Pathway III (link), via glutamate mutase, is not included because the first step (glutamate mutase, EC 5.4.99.1) has not been linked to sequence and because no organism has been demonstrated to rely on this pathway to form oxobutanoate. MetaCyc L-isoleucine biosynthesis V describes biosynthesis from 2-methylbutanoate, which is a fermentation end product in the rumen; this is an an unusual precursor so we did not include it.
Or see definitions of steps
| Step | Description | Best candidate | 2nd candidate |
|---|---|---|---|
| ilvA | threonine deaminase | BTUS_RS02985 | BTUS_RS07370 |
| ilvI | acetolactate/acetohydroxybutanoate synthase catalytic subunit | BTUS_RS04765 | BTUS_RS01430 |
| ilvH | acetolactate/acetohydroxybutanoate synthase regulatory subunit | BTUS_RS04770 | |
| ilvC | 2-hydroxy-3-ketol-acid reductoisomerase | BTUS_RS04775 | |
| ilvD | dihydroxy-acid dehydratase | BTUS_RS05140 | |
| ilvE | isoleucine transaminase | BTUS_RS04760 | BTUS_RS01285 |
| Alternative steps: | |||
| cimA | (R)-citramalate synthase | BTUS_RS04780 | |
| leuB | 3-methylmalate dehydrogenase / 3-isopropylmalate dehydrogenase | BTUS_RS04785 | BTUS_RS15235 |
| leuC | 3-isopropylmalate dehydratase / citramalate isomerase, large subunit | BTUS_RS11945 | BTUS_RS12735 |
| leuD | 3-isopropylmalate dehydaratase / citramalate isomerase, small subunit | BTUS_RS11950 | |
| ofoa | 2-oxobutanoate:ferredoxin oxidoreductase, alpha subunit | BTUS_RS02485 | |
| ofob | 2-oxobutanoate:ferredoxin oxidoreductase, beta subunit | BTUS_RS02480 | |
| prpE | propionyl-CoA synthetase | BTUS_RS08765 | BTUS_RS03965 |
Confidence: high confidence medium confidence low confidence
? – known gap: despite the lack of a good candidate for this step, this organism (or a related organism) performs the pathway
This GapMind analysis is from Apr 10 2024. The underlying query database was built on Apr 09 2024.
Each pathway is defined by a set of rules based on individual steps or genes. Candidates for each step are identified by using ublast (a fast alternative to protein BLAST) against a database of manually-curated proteins (most of which are experimentally characterized) or by using HMMer with enzyme models (usually from TIGRFam). Ublast hits may be split across two different proteins.
A candidate for a step is "high confidence" if either:
Otherwise, a candidate is "medium confidence" if either:
Other blast hits with at least 50% coverage are "low confidence."
Steps with no high- or medium-confidence candidates may be considered "gaps." For the typical bacterium that can make all 20 amino acids, there are 1-2 gaps in amino acid biosynthesis pathways. For diverse bacteria and archaea that can utilize a carbon source, there is a complete high-confidence catabolic pathway (including a transporter) just 38% of the time, and there is a complete medium-confidence pathway 63% of the time. Gaps may be due to:
GapMind relies on the predicted proteins in the genome and does not search the six-frame translation. In most cases, you can search the six-frame translation by clicking on links to Curated BLAST for each step definition (in the per-step page).
For more information, see:
If you notice any errors or omissions in the step descriptions, or any questionable results, please let us know
by Morgan Price, Arkin group, Lawrence Berkeley National Laboratory