ECI1 (YLR284C) encodes the peroxisomal Delta(3)-cis-Delta(2)-trans-enoyl-CoA isomerase (EC 5.3.3.8), an auxiliary enzyme of beta-oxidation of unsaturated fatty acids that converts 3-cis- (and 3-trans-) enoyl-CoA intermediates, formed when beta-oxidation reaches a double bond at an odd-numbered position, into 2-trans-enoyl-CoAs that re-enter the core cycle. The purified recombinant protein is a homohexamer (dimer of trimers) of ~32 kDa subunits belonging to the enoyl-CoA hydratase/isomerase (crotonase) family, and it lacks the catalytic glutamate conserved in most family members. ECI1 is oleate-induced through an oleate response element bound by Oaf1p/Pip2p. Deletion abolishes cellular 3,2-isomerase activity and growth on oleic acid but not on saturated palmitic acid, establishing Eci1p as the essential isomerase of the isomerase-dependent route. Eci1p resides in the peroxisomal matrix; it interacts with its paralog Dci1p and can be imported via its own PTS1 or piggy-back with Dci1p.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from the PANTHER enoyl-CoA isomerase node (PTN000234739) whose donors include yeast Eci1p and mammalian ECI1/ECI2. Consistent with direct biochemical evidence for Eci1p. Supporting Evidence: PMID:9813046 It was found to be a hexameric protein with a subunit of molecular mass 32, 000 Da that converted 3-hexenoyl-CoA to trans-2-hexenoyl-CoA PMID:9837886 a bacterially expressed form of this protein catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 16 units/mg |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IDA PMID:9813046 Peroxisomal Delta3-cis-Delta2-trans-enoyl-CoA isomerase enco... | ACCEPT | Summary: IDA (Gurvitz et al. 1998): purified recombinant Eci1p converted 3-hexenoyl-CoA to trans-2-hexenoyl-CoA. Supporting Evidence: PMID:9813046 It was found to be a hexameric protein with a subunit of molecular mass 32, 000 Da that converted 3-hexenoyl-CoA to trans-2-hexenoyl-CoA |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IDA PMID:9837886 Molecular characterization of Saccharomyces cerevisiae Delta... | ACCEPT | Summary: IDA (Geisbrecht et al. 1998): bacterially expressed Eci1p isomerised 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA at 16 U/mg. Supporting Evidence: PMID:9837886 a bacterially expressed form of this protein catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 16 units/mg |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from Rhea/EC 5.3.3.8 mapping of UniProt catalytic activities; matches the experimentally established activity. Supporting Evidence: file:yeast/ECI1/ECI1-uniprot.txt Reaction=a (3Z)-enoyl-CoA = a 4-saturated (2E)-enoyl-CoA |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IMP PMID:9813046 Peroxisomal Delta3-cis-Delta2-trans-enoyl-CoA isomerase enco... | ACCEPT | Summary: IMP (Gurvitz et al. 1998): loss of Eci1p abolishes growth on unsaturated (but not saturated) fatty acids, and rescue by the rat isomerase-containing MFE-1 links the defect to loss of 3,2-isomerase activity. Supporting Evidence: PMID:9813046 A mutant devoid of Eci1p was unable to grow on media containing unsaturated fatty acids such as oleic acid but was proficient for growth when a saturated fatty acid such as palmitic acid was the sole carbon source PMID:9813046 Rat peroxisomal multifunctional enzyme type I containing Delta3-cis-Delta2-trans-enoyl-CoA isomerase activity was expressed in ECI1-deleted yeast cells, and this restored growth on oleic acid |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | IMP PMID:9837886 Molecular characterization of Saccharomyces cerevisiae Delta... | ACCEPT | Summary: IMP (Geisbrecht et al. 1998): cells lacking YLR284C/ECI1 had no detectable Delta3,Delta2-enoyl-CoA isomerase activity. Supporting Evidence: PMID:9837886 Cells lacking YLR284C had no detectable Delta3,Delta2-enoyl-CoA isomerase activity |
| GO:0004165 delta(3)-delta(2)-enoyl-CoA isomerase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (YEAST-FAO-PWY) assigning Eci1p to the EC 5.3.3.8 step of fatty acid oxidation. Correct: this is the step Eci1p catalyses, with direct biochemical and genetic evidence. Supporting Evidence: PMID:9837886 a bacterially expressed form of this protein catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 16 units/mg PMID:9837886 Cells lacking YLR284C had no detectable Delta3,Delta2-enoyl-CoA isomerase activity |
| GO:0005777 peroxisome | IDA PMID:9813046 Peroxisomal Delta3-cis-Delta2-trans-enoyl-CoA isomerase enco... | ACCEPT | Summary: IDA (Gurvitz et al. 1998): an Eci1p-GFP fusion localised to peroxisomes in wild-type cells. Supporting Evidence: PMID:9813046 Using a green fluorescent protein fusion, Eci1p was shown to be located in peroxisomes of wild-type yeast cells |
| GO:0005777 peroxisome | IDA PMID:9837886 Molecular characterization of Saccharomyces cerevisiae Delta... | ACCEPT | Summary: IDA (Geisbrecht et al. 1998): Eci1p localises to peroxisomes in a PEX8-dependent manner. Supporting Evidence: PMID:9837886 localizes to the peroxisome in a PEX8-dependent manner |
| GO:0005777 peroxisome | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from UniProt subcellular location (SL-0204, peroxisome); consistent with the experimental localisation data. Supporting Evidence: file:yeast/ECI1/ECI1-uniprot.txt SUBCELLULAR LOCATION: Peroxisome |
| GO:0005782 peroxisomal matrix | IBA GO_REF:0000033 | ACCEPT | Summary: IBA for peroxisomal matrix (is_active_in) from the ECI family node. Eci1p is a soluble beta-oxidation enzyme imported into the matrix; consistent with the yeast data. Supporting Evidence: PMID:9813046 Using a green fluorescent protein fusion, Eci1p was shown to be located in peroxisomes of wild-type yeast cells |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA from YEAST-FAO-PWY places fatty acid oxidation in the cytosol. In yeast beta-oxidation is exclusively peroxisomal and Eci1p is a peroxisomal enzyme; the cytosol assignment is a conversion artefact. Supporting Evidence: PMID:9813046 Using a green fluorescent protein fusion, Eci1p was shown to be located in peroxisomes of wild-type yeast cells PMID:9837886 localizes to the peroxisome in a PEX8-dependent manner |
| GO:0006635 fatty acid beta-oxidation | IBA GO_REF:0000033 | ACCEPT | Summary: IBA for fatty acid beta-oxidation from the ECI family node; Eci1p is the essential auxiliary isomerase for beta-oxidation of unsaturated fatty acids. Supporting Evidence: PMID:9813046 A mutant devoid of Eci1p was unable to grow on media containing unsaturated fatty acids such as oleic acid but was proficient for growth when a saturated fatty acid such as palmitic acid was the sole carbon source |
| GO:0006635 fatty acid beta-oxidation | IDA PMID:9813046 Peroxisomal Delta3-cis-Delta2-trans-enoyl-CoA isomerase enco... | ACCEPT | Summary: IDA (Gurvitz et al. 1998) for beta-oxidation: Eci1p is required for growth on oleate and catalyses the 3,2-isomerisation step. Supporting Evidence: PMID:9813046 A mutant devoid of Eci1p was unable to grow on media containing unsaturated fatty acids such as oleic acid but was proficient for growth when a saturated fatty acid such as palmitic acid was the sole carbon source PMID:9813046 It was found to be a hexameric protein with a subunit of molecular mass 32, 000 Da that converted 3-hexenoyl-CoA to trans-2-hexenoyl-CoA |
| GO:0006635 fatty acid beta-oxidation | IDA PMID:9837886 Molecular characterization of Saccharomyces cerevisiae Delta... | ACCEPT | Summary: IDA (Geisbrecht et al. 1998): Eci1p catalyses the 3,2-isomerisation and is required for growth on oleate, placing it in beta-oxidation of unsaturated fatty acids. Supporting Evidence: PMID:9837886 Removal of YLR284C from the S. cerevisiae genome eliminated growth on oleic acid, but had no effect on peroxisome biogenesis, indicating a role for YLR284C in fatty acid metabolism PMID:9837886 a bacterially expressed form of this protein catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 16 units/mg |
| GO:0006635 fatty acid beta-oxidation | IEA GO_REF:0000041 | ACCEPT | Summary: IEA from UniPathway UPA00659 (fatty acid beta-oxidation); correct. Supporting Evidence: file:yeast/ECI1/ECI1-uniprot.txt PATHWAY: Lipid metabolism; fatty acid beta-oxidation |
| GO:0019395 fatty acid oxidation | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA for fatty acid oxidation; correct parent of fatty acid beta-oxidation, the process in which Eci1p acts. Supporting Evidence: PMID:9813046 A mutant devoid of Eci1p was unable to grow on media containing unsaturated fatty acids such as oleic acid but was proficient for growth when a saturated fatty acid such as palmitic acid was the sole carbon source |
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Download this section (compressed HTML)Q: How does Eci1p catalyse isomerisation without the catalytic glutamate conserved in other crotonase-family isomerases, and which residue substitutes as the proton donor/acceptor?
Q: Is the Eci1p-Dci1p interaction a stable hetero-hexamer in the matrix, or only a transient import (piggy-back) association?
Experiment: Solve the Eci1p structure with a 3-enoyl-CoA analogue and test site-directed mutants of candidate active-site residues for 3,2-isomerase activity and complementation of eci1 growth on oleate.
Hypothesis: A non-glutamate residue in the Eci1p active site provides the catalytic base.
Peroxisomal delta3,delta2-enoyl-CoA isomerase; hexameric protein that converts 3-hexenoyl-CoA to trans-2-hexenoyl-CoA, essential for the beta-oxidation of unsaturated fatty acids, oleate-induced; ECI1 has a paralog, DCI1, that arose from the whole genome duplication
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