HEM15 encodes ferrochelatase (protoheme ferro-lyase, EC 4.98.1.1, formerly 4.99.1.1), the terminal enzyme of heme biosynthesis. It inserts Fe2+ into protoporphyrin IX to form protoheme (heme b). The nuclear-encoded precursor carries a 31-residue N-terminal mitochondrial presequence. The mature 40.9 kDa protein is a peripheral protein of the inner mitochondrial membrane with its active site facing the matrix, where it receives protoporphyrin IX from protoporphyrinogen oxidase (Hem14p). hem15 mutants accumulate protoporphyrin IX and are heme-deficient, and the purified enzyme shows ferrochelatase kinetics with porphyrin and iron substrates. Correct matrix-side localization is needed for efficient heme and b-type cytochrome production: a version lacking the targeting sequence still chelates iron but mislocalizes to other membranes and supports less heme synthesis. HEM15 is only mildly repressed by glucose.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004325 protoporphyrin ferrochelatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PANTHER node PTN000121751 (ferrochelatase family, PTHR11108), whose experimental sources include HEM15 itself (SGD:S000005702), human FECH and mouse Fech. Hem15p is a canonical member of the clade and retains the catalytic machinery; the inherited activity is correct. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt PANTHER; PTHR11108; FERROCHELATASE; 1. file:yeast/HEM15/HEM15-uniprot.txt Reaction=heme b + 2 H(+) = protoporphyrin IX + Fe(2+); PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. |
| GO:0004325 protoporphyrin ferrochelatase activity | IDA PMID:1304908 Yeast ferrochelatase: expression in a baculovirus system and... | ACCEPT | Summary: Eldridge & Dailey expressed yeast Hem15p in a baculovirus system and purified active enzyme, measuring Km values for the porphyrin (mesoporphyrin) and iron substrates; this is direct biochemical evidence for ferrochelatase activity of the HEM15 product. Supporting Evidence: PMID:1304908 This system is shown to be an excellent one in which to produce large quantities of active ferrochelatase. PMID:1304908 The measured Km's for the substrates mesoporphyrin and iron are the same as those reported previously for the yeast enzyme. |
| GO:0004325 protoporphyrin ferrochelatase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA (ARBA rule, InterPro IPR001015/IPR019772 ferrochelatase signatures, RHEA:22584, EC 4.98.1.1). The mapping is correct for Hem15p and is backed by experimental evidence; EC 4.99.1.1 was transferred to 4.98.1.1 without change of reaction. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt Reaction=heme b + 2 H(+) = protoporphyrin IX + Fe(2+); |
| GO:0004325 protoporphyrin ferrochelatase activity | IMP PMID:2185242 The ferrochelatase from Saccharomyces cerevisiae. Sequence, ... | ACCEPT | Summary: Labbe-Bois cloned HEM15 by complementation of a ferrochelatase-deficient hem15 mutant and showed it encodes the mitochondrial ferrochelatase that inserts Fe2+ into protoporphyrin IX; core activity. Supporting Evidence: PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. PMID:2185242 The gene was isolated by functional complementation of a hem15 mutant. |
| GO:0004325 protoporphyrin ferrochelatase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA from PWY3O-69 (superpathway of heme and siroheme biosynthesis): protoporphyrin IX + Fe2+ -> ferroheme b + 2 H+ (EC 4.99.1.1/4.98.1.1). This is exactly the reaction Hem15p catalyses; correct gene-reaction assignment. Supporting Evidence: PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | ACCEPT | Summary: High-throughput detection of Hem15p in purified mitochondria in the PROMITO mitochondrial proteome (Reinders et al. 2006). Organelle proteomics cannot resolve the sub-compartment, so the root organelle row is accepted; the inner-membrane location is captured by the separate GO:0005743 rows. Supporting Evidence: PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane PMID:16823961 A total of 851 different proteins (PROMITO dataset) were identified by use of multidimensional LC-MS/MS |
| GO:0005739 mitochondrion | HDA PMID:24769239 Quantitative variations of the mitochondrial proteome and ph... | ACCEPT | Summary: High-throughput detection of Hem15p in purified mitochondria in the quantitative mitochondrial proteome of fermentative and respiratory cells (Renvoise et al. 2014). Accepted at the organelle level; the inner-membrane location is captured by the GO:0005743 rows. Supporting Evidence: PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane PMID:24769239 we performed an overall quantitative proteomic and phosphoproteomic study of isolated mitochondria |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: IBA is_active_in mitochondrion from PTN008512544 (eukaryotic ferrochelatases; IBD seeds HEM15, mouse Fech, human FECH and Arabidopsis FC1). Checked the seeds: all are organellar ferrochelatases, and Hem15p is imported and acts on the matrix side of the inner membrane (PMID:7629135). The organelle claim holds; the sub-compartment is captured by the GO:0005743 rows. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt PANTHER; PTHR11108; FERROCHELATASE; 1. PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane file:yeast/HEM15/HEM15-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion inner membrane; Peripheral membrane |
| GO:0005743 mitochondrial inner membrane | IDA PMID:7629135 Effect of cellular location on the function of ferrochelatas... | ACCEPT | Summary: Prasad & Dailey showed by fractionation that full-length Hem15p is imported and sits on the matrix side of the inner mitochondrial membrane, whereas a variant lacking the targeting sequence mislocalises to other membranes and supports less heme and b-type cytochrome synthesis. This supports both located_in and is_active_in for the inner membrane; core location. Supporting Evidence: PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane PMID:7629135 In cells containing the truncated construct, ferrochelatase activity was found in all membrane fractions but was not located on the matrix side of the inner mitochondrial membrane. |
| GO:0005743 mitochondrial inner membrane | IDA PMID:7629135 Effect of cellular location on the function of ferrochelatas... | ACCEPT | Summary: Prasad & Dailey showed by fractionation that full-length Hem15p is imported and sits on the matrix side of the inner mitochondrial membrane, whereas a variant lacking the targeting sequence mislocalises to other membranes and supports less heme and b-type cytochrome synthesis. This supports both located_in and is_active_in for the inner membrane; core location. Supporting Evidence: PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane PMID:7629135 In cells containing the truncated construct, ferrochelatase activity was found in all membrane fractions but was not located on the matrix side of the inner mitochondrial membrane. |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0168, Mitochondrion inner membrane; peripheral, matrix side). Correct and matches the experimental data. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion inner membrane; Peripheral membrane PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA is_active_in cytosol from PWY3O-69 (superpathway of heme and siroheme biosynthesis). The pathway-to-GO-CAM conversion placed all steps in the cytosol by default, but Hem15p is imported into mitochondria and its activity is on the matrix side of the inner membrane; mislocalisation to non-mitochondrial membranes impairs heme and cytochrome b production. The cytosolic location is wrong for this enzyme. Reason: Experimental evidence places ferrochelatase activity on the matrix face of the inner mitochondrial membrane (GO:0005743), not in the cytosol. Supporting Evidence: PMID:7629135 is synthesized in the cytoplasm in a precursor form and then is translocated to the matrix side of the inner mitochondrial membrane PMID:7629135 In cells containing the truncated construct, ferrochelatase activity was found in all membrane fractions but was not located on the matrix side of the inner mitochondrial membrane. |
| GO:0006783 heme biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000121751 (ferrochelatase family; HEM15 among the experimental sources). Ferrochelatase catalyses the terminal step of protoheme synthesis in all heme-synthesising organisms; correct core process. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt PANTHER; PTHR11108; FERROCHELATASE; 1. PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. |
| GO:0006783 heme biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO mapping from the ferrochelatase signatures (IPR001015, IPR019772). Correct for Hem15p, which catalyses the last step of heme biosynthesis. Supporting Evidence: file:yeast/HEM15/HEM15-uniprot.txt FUNCTION: Catalyzes the ferrous insertion into protoporphyrin IX. |
| GO:0006783 heme biosynthetic process | IMP PMID:7035824 Genetic and biochemical characterization of mutants of Sacch... | ACCEPT | Summary: Urban-Grimal & Labbe-Bois characterised heme-deficient mutants blocked in six distinct steps, including a mutant lacking ferrochelatase activity; loss of this activity blocks heme synthesis. Hem15p catalyses the terminal step, so this is a core process. Supporting Evidence: PMID:7035824 Six of the seven mutants were blocked in a different enzyme activity: 5-aminolevulinate synthase, porphobilinogen synthase, uroporphyrinogen I synthase, uroporphyrinogen decarboxylase, coproporphyrinogen III oxidase and ferrochelatase. |
| GO:0006783 heme biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA from HEME-BIOSYNTHESIS-II (heme b biosynthesis I (aerobic)). Hem15p catalyses the final step of heme b synthesis, so heme biosynthetic process is correct for this enzyme (not a superpathway inflation). Supporting Evidence: PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. |
| GO:0006783 heme biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA from PWY3O-69 (superpathway of heme and siroheme biosynthesis). Hem15p catalyses the final step of heme b synthesis, so heme biosynthetic process is correct for this enzyme (not a superpathway inflation). Supporting Evidence: PMID:2185242 The HEM15 gene in Saccharomyces cerevisiae encodes ferrochelatase (EC 4.99.1.1, protoheme ferrolyase), a mitochondrial inner membrane-bound enzyme which catalyzes the insertion of ferrous ion into protoporphyrin IX, the last step in protoheme biosynthesis. |
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Download this section (compressed HTML)Q: Does Hem15p form a physical complex with Hem14p (protoporphyrinogen oxidase) and the mitochondrial iron delivery machinery (e.g. Mrs3/Mrs4 carriers or frataxin Yfh1) in yeast, as proposed for mammalian ferrochelatase?
Q: Does yeast ferrochelatase contain an iron-sulfur cluster like the mammalian enzyme, or is it cluster-free like bacterial ferrochelatases?
Experiment: Use crosslinking/affinity purification of tagged Hem15p from isolated mitochondria followed by mass spectrometry, and test substrate channelling by measuring free protoporphyrin IX release in reconstituted Hem14p-Hem15p systems.
Hypothesis: Hem15p channels protoporphyrin IX directly from Hem14p and receives iron from a dedicated mitochondrial donor
Type: protein interaction / enzymology
Ferrochelatase; a mitochondrial inner membrane protein, catalyzes insertion of ferrous iron into protoporphyrin IX, the eighth and final step in the heme biosynthetic pathway; human homolog FECH can complement yeast mutant and allow growth of haploid null after sporulation of a heterozygous diploid
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