Dihydroxy-acid dehydratase (DHAD, EC 4.2.1.9) of fission yeast, encoded by SPAC17G8.06c (ilv3+) and orthologous to S. cerevisiae ILV3 and bacterial IlvD. It is an iron-sulfur cluster enzyme of the IlvD/EDD family. It dehydrates (2R)-2,3-dihydroxy-3-methylbutanoate to 2-oxoisovalerate (precursor of valine and leucine) and (2R,3R)-2,3-dihydroxy-3-methylpentanoate to (S)-3-methyl-2-oxopentanoate (precursor of isoleucine). It acts in mitochondria after ketol-acid reductoisomerase (ilv5). The deletion mutant needs branched-chain amino acids and is rescued by S. cerevisiae ILV3. The mutant also fails to grow on EMM even when Leu, Ile and Val are supplied, which points to an additional, unexplained requirement on that medium.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro (IPR020558, DHAD/6-phosphogluconate dehydratase signature) mapped to the root catalytic activity; true but uninformative. Reason: Replace with the specific dihydroxy-acid dehydratase activity. Proposed replacements: dihydroxy-acid dehydratase activity Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in |
| GO:0004160 dihydroxy-acid dehydratase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA (PTN000470221) whose donors include S. pombe SPAC17G8.06c itself (via its IMP annotation), S. cerevisiae ILV3, Arabidopsis DHAD and M. tuberculosis IlvD. The self-reference reflects the gene's own experimental grounding. Core MF. Supporting Evidence: PMID:35325114 This finding suggests that S. pombe SPAC17G8.06c is a functional ortholog of S. cerevisiae ILV3 and encodes a dihydroxy-acid dehydratase. file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in |
| GO:0004160 dihydroxy-acid dehydratase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA (ARBA, IPR004404, RHEA:24809/27694, EC 4.2.1.9); correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in |
| GO:0004160 dihydroxy-acid dehydratase activity | IMP PMID:35325114 Response to leucine in Schizosaccharomyces pombe (fission ye... | ACCEPT | Summary: Ohtsuka et al. deleted SPAC17G8.06c, showed BCAA-dependent growth defects and rescued them with S. cerevisiae ILV3 (DHAD) as well as the S. pombe gene. Cross-species complementation by a characterised DHAD supports the activity, although the enzyme was not assayed directly. Defer to the PomBase curator. Supporting Evidence: PMID:35325114 The defective growth of the ΞSPAC17G8.06c mutant was complemented not only by the expression of S. pombe SPAC17G8.06c itself but also by the S. cerevisiae ILV3. PMID:35325114 This finding suggests that S. pombe SPAC17G8.06c is a functional ortholog of S. cerevisiae ILV3 and encodes a dihydroxy-acid dehydratase. |
| GO:0004160 dihydroxy-acid dehydratase activity | ISS GO_REF:0000024 | ACCEPT | Summary: ISS from E. coli IlvD (P05791); ilv3 carries the full IlvD/EDD architecture (TIGR00110). Correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in |
| GO:0004160 dihydroxy-acid dehydratase activity | ISS GO_REF:0000024 | ACCEPT | Summary: ISS from S. cerevisiae ILV3 (P39522), the functionally complementing ortholog; correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in PMID:35325114 The defective growth of the ΞSPAC17G8.06c mutant was complemented not only by the expression of S. pombe SPAC17G8.06c itself but also by the S. cerevisiae ILV3. |
| GO:0005739 mitochondrion | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome-wide YFP localisation placed ilv3 in mitochondria, as cited by the 2022 review; consistent with its predicted presequence. Supporting Evidence: PMID:35325114 Like ALS and Ilv5, Ilv3 is also localized in the mitochondria |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA (PTN001077098, seeded by S. cerevisiae ILV3) for mitochondrion; agrees with the HDA. Supporting Evidence: PMID:35325114 Like ALS and Ilv5, Ilv3 is also localized in the mitochondria |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (Mitochondrion, by similarity to P39522); correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion {ECO:0000250|UniProtKB:P39522}. |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | ACCEPT | Summary: ISS from S. cerevisiae ILV3 for mitochondrial location; consistent with the S. pombe HDA. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion {ECO:0000250|UniProtKB:P39522}. PMID:35325114 Like ALS and Ilv5, Ilv3 is also localized in the mitochondria |
| GO:0005759 mitochondrial matrix | IC GO_REF:0000111 | ACCEPT | Summary: PomBase curator inference (from GO:0004160) of activity in the mitochondrial matrix, the compartment of the fungal BCAA trunk; used in the PomBase GO-CAM. Supporting Evidence: PMID:35325114 Like ALS and Ilv5, Ilv3 is also localized in the mitochondria |
| GO:0009082 branched-chain amino acid biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for branched-chain amino acid biosynthesis; ilv3 catalyses the third shared step. Supporting Evidence: PMID:35325114 The deletion mutant of SPAC17G8.06c can grow in yeast extract complete medium but cannot grow in Edinburgh minimal medium (EMM) with Leu. This is because this gene is involved in the synthesis of Leu as well as Ile and Val. |
| GO:0009082 branched-chain amino acid biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro (IPR004404) mapping to branched-chain amino acid biosynthesis; correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt FUNCTION: Dihydroxyacid dehydratase that catalyzes the third step in |
| GO:0009098 L-leucine biosynthetic process | IMP PMID:35325114 Response to leucine in Schizosaccharomyces pombe (fission ye... | ACCEPT | Summary: The deletion cannot grow on minimal medium with leucine alone; ilv3 makes 2-oxoisovalerate, the substrate of leu3, so it performs a step of the leucine route. The PomBase GO-CAM places the leucine-branch ilv3 activity causally upstream of leu3. Supporting Evidence: PMID:35325114 The deletion mutant of SPAC17G8.06c can grow in yeast extract complete medium but cannot grow in Edinburgh minimal medium (EMM) with Leu. This is because this gene is involved in the synthesis of Leu as well as Ile and Val. |
| GO:0009099 L-valine biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway mapping (L-valine biosynthesis step 3/4); correct. Supporting Evidence: file:SCHPO/ilv3/ilv3-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-valine biosynthesis; L-valine from |
| GO:0009099 L-valine biosynthetic process | IMP PMID:35325114 Response to leucine in Schizosaccharomyces pombe (fission ye... | ACCEPT | Summary: Deletion phenotype and complementation by S. cerevisiae ILV3 support a role in valine synthesis; DHAD converts 2,3-dihydroxy-3-methylbutanoate to 2-oxoisovalerate. Supporting Evidence: PMID:35325114 The deletion mutant of SPAC17G8.06c can grow in yeast extract complete medium but cannot grow in Edinburgh minimal medium (EMM) with Leu. This is because this gene is involved in the synthesis of Leu as well as Ile and Val. PMID:35325114 are then converted by dihydroxy-acid dehydratase to 3-methyl-2-oxobutanoate and (S)-3-methyl-2-oxopentanoate, respectively |
| GO:1901705 L-isoleucine biosynthetic process | IMP PMID:35325114 Response to leucine in Schizosaccharomyces pombe (fission ye... | ACCEPT | Summary: Deletion phenotype and complementation support a role in isoleucine synthesis; DHAD converts 2,3-dihydroxy-3-methylpentanoate to (S)-3-methyl-2-oxopentanoate. Supporting Evidence: PMID:35325114 The deletion mutant of SPAC17G8.06c can grow in yeast extract complete medium but cannot grow in Edinburgh minimal medium (EMM) with Leu. This is because this gene is involved in the synthesis of Leu as well as Ile and Val. PMID:35325114 are then converted by dihydroxy-acid dehydratase to 3-methyl-2-oxobutanoate and (S)-3-methyl-2-oxopentanoate, respectively |
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Download this section (compressed HTML)Experiment: Test whether pantothenate, 2-oxoisovalerate or a change of nitrogen source (ammonium chloride versus glutamate) rescues growth of ilv3 deletion cells on EMM plus Leu/Ile/Val.
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The ilv3 deletion cannot grow on Edinburgh minimal medium even when leucine, isoleucine and valine are supplied, although it grows on synthetic dextrose medium with these amino acids. The basis of this medium-specific requirement is unknown.
OPEN BIOLOGY
What is known: Established: BCAA auxotrophy and rescue by S. cerevisiae ILV3. Unknown: whether the EMM defect reflects pantothenate/CoA precursor (2-oxoisovalerate) limitation, a nitrogen-source effect on BCAA uptake, or a non-catalytic role of ilv3.
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