Ech1 (CG9577) is a Drosophila melanogaster delta(3,5),delta(2,4)-dienoyl-CoA isomerase (EC 5.3.3.21), an auxiliary enzyme of the beta-oxidation of polyunsaturated fatty acids that have a double bond at an odd-numbered carbon. It isomerizes 3-trans,5-cis-dienoyl-CoA (3E,5Z-dienoyl-CoA) to 2-trans,4-trans-dienoyl-CoA (2E,4E-dienoyl-CoA), which is then reduced by 2,4-dienoyl-CoA reductase and re-isomerized by the delta(3),delta(2)-enoyl-CoA isomerase to rejoin the core beta-oxidation spiral. Ech1 is the ortholog of human ECH1; its subcellular localization is not fully resolved in the fly - UniProt names it mitochondrial and phylogenetic/orthology evidence places it in the mitochondrion, while an electronic and a targeting-signal prediction also assign it to the peroxisome (human ECH1 is peroxisomal), so a dual or organism-specific localization is plausible.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetically inferred mitochondrial localization, consistent with the UniProt "mitochondrial" naming of Ech1 and with a role in the mitochondrial beta-oxidation of polyunsaturated fatty acids. Reason: Mitochondrion is the primary annotated compartment for fly Ech1; retained as the core location (see the peroxisome annotations for the alternative/dual localization). |
| GO:0051750 delta(3,5)-delta(2,4)-dienoyl-CoA isomerase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetically inferred delta(3,5),delta(2,4)-dienoyl-CoA isomerase activity (EC 5.3.3.21) - the defining molecular function of Ech1 and the auxiliary step for polyunsaturated fatty acid beta-oxidation. Reason: Core molecular function of Ech1, concordant with the EC/UniProt name and the IEA evidence. Supporting Evidence: file:DROME/Ech1/Ech1-uniprot.txt Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase, mitochondrial |
| GO:0005737 cytoplasm | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA electronic cytoplasm annotation. Ech1 is an organellar (mitochondrial/peroxisomal) beta-oxidation enzyme; "cytoplasm" is an over-general parent that does not capture the compartment. Reason: Uninformative over-general term superseded by the specific mitochondrion/peroxisome localization annotations. |
| GO:0005777 peroxisome | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Electronic (UniProt subcellular-location) peroxisome annotation. Human ECH1 is peroxisomal, so a peroxisomal pool of fly Ech1 is plausible, but the fly protein is primarily annotated mitochondrial; the localization is unresolved. Reason: Possible dual/alternative localization; retained as non-core relative to the mitochondrion pending direct evidence resolving the mitochondrion-vs-peroxisome assignment. |
| GO:0016853 isomerase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro electronic annotation to the parent isomerase class. Correct but a high-level parent of the specific dienoyl-CoA isomerase activity. Reason: Accurate parent term subsumed by the specific delta(3,5),delta(2,4)-dienoyl-CoA isomerase activity. |
| GO:0051750 delta(3,5)-delta(2,4)-dienoyl-CoA isomerase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Electronic assignment of the EC 5.3.3.21 dienoyl-CoA isomerase activity, duplicating the core molecular-function call. Reason: Core molecular function of Ech1. Supporting Evidence: file:DROME/Ech1/Ech1-uniprot.txt Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase, mitochondrial |
| GO:0006635 fatty acid beta-oxidation | IEA GO_REF:0000041 | ACCEPT | Summary: Electronic annotation to fatty acid beta-oxidation - specifically the auxiliary dienoyl-CoA isomerase step required to fully degrade polyunsaturated fatty acids. Reason: Core biological process for Ech1 as an auxiliary enzyme of (polyunsaturated) fatty acid beta-oxidation. |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | ACCEPT | Summary: Orthology-based mitochondrial localization, concordant with the UniProt mitochondrial naming and the IBA mitochondrion call. Reason: Mitochondrion is the primary annotated compartment for fly Ech1; core location. |
| GO:0005777 peroxisome | ISM PMID:22758915 An inventory of peroxisomal proteins and pathways in Drosoph... | KEEP AS NON CORE | Summary: Sequence-model (targeting-signal) prediction of peroxisomal localization from the Drosophila peroxisomal-proteome inventory. Consistent with the peroxisomal localization of human ECH1 but in tension with the mitochondrial naming; localization remains unresolved. Reason: Possible dual/alternative localization; retained as non-core relative to the mitochondrion pending experimental resolution. Supporting Evidence: PMID:22758915 The subcellular localization of five of these predicted peroxisomal proteins was confirmed. |
| GO:0006635 fatty acid beta-oxidation | NAS PMID:22758915 An inventory of peroxisomal proteins and pathways in Drosoph... | ACCEPT | Summary: Author statement associating Ech1 with fatty acid beta-oxidation in the peroxisomal-proteome inventory, concordant with its dienoyl-CoA isomerase role. Reason: Core biological process for Ech1 in (polyunsaturated) fatty acid beta-oxidation. Supporting Evidence: PMID:22758915 An inventory of peroxisomal proteins and pathways in Drosophila melanogaster |
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Download this section (compressed HTML)Q: Is Drosophila Ech1 mitochondrial (as its UniProt name and phylogenetic annotation indicate), peroxisomal (as for human ECH1 and the targeting-signal prediction), or dually localized - and which pool supports the mitochondrial polyunsaturated-FAO cassette?
Experiment: Tagged-protein localization / organelle fractionation of Ech1 to resolve its mitochondrial versus peroxisomal distribution, and an in-vitro assay of recombinant Ech1 on 3E,5Z-dienoyl-CoA to confirm the delta(3,5),delta(2,4)-dienoyl-CoA isomerase activity.
Hypothesis: Fly Ech1 provides the dienoyl-CoA isomerase step of polyunsaturated fatty acid beta-oxidation, with a mitochondrial pool serving the mitochondrial cassette even if a peroxisomal pool also exists.
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