AN1593 encodes a short HMG-CoA reductase in the PbcR-activated Aspergillus nidulans pimaradiene biosynthetic cluster. The protein retains the class I HMG-CoA reductase catalytic domain and residues but lacks the N-terminal sterol-sensing membrane region of canonical fungal sterol-pathway HMG-CoA reductases. It is proposed to reduce HMG-CoA to mevalonate and to supply mevalonate-derived isoprenoid precursors for production of the diterpene ent-pimara-8(14),15-diene.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004420 hydroxymethylglutaryl-CoA reductase (NADPH) activity | IBA GO_REF:0000033 | ACCEPT | Summary: HMG-CoA reductase activity inherited from PAINT node PTN000060346. Correct. Reason: AN1593 belongs to the HMG-CoA reductase family and was identified as the HMG-CoA reductase encoded within the PbcR-activated pimaradiene biosynthetic cluster. PAINT node PTN000060346 places the exact NADPH-dependent HMG-CoA reductase activity above the AN1593-containing HMG-CoA reductase family, which is appropriate because AN1593 retains the catalytic family signature even though its organismal role is secondary diterpene metabolism rather than housekeeping ergosterol production. Supporting Evidence: file:interpro/panther/PTHR10572/PTHR10572-paint.tsv PTHR10572 PTN000060346 GO:0004420 F IBD false file:genes/EMENI/AN1593/AN1593-uniprot.txt Belongs to the HMG-CoA reductase family. {ECO:0000305}. file:genes/EMENI/AN1593/AN1593-uniprot.txt NCBIfam; TIGR00533; HMG_CoA_R_NADP; 1. file:genes/EMENI/AN1593/AN1593-uniprot.txt PROSITE; PS50065; HMG_COA_REDUCTASE_4; 1. file:genes/EMENI/AN1593/AN1593-uniprot.txt ACT_SITE 408 FT /note="Proton donor" PMID:22506079 Based on the data presented here, we suggest a model for ent-pimara-8(14),15-diene biosynthesis in Aspergillus nidulans. Specifically, HMG-CoA reductase (AN1593.4) functions in the mevalonate pathway, which produces isoprenoid precursors. |
| GO:0004420 hydroxymethylglutaryl-CoA reductase (NADPH) activity | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro/Rhea/EC mapping to exact HMG-CoA reductase activity. Correct. Reason: The InterPro signatures, RHEA reaction, and EC 1.1.1.34 identify AN1593 as a class I NADPH-dependent HMG-CoA reductase, and the A. nidulans pimaradiene study specifically names AN1593.4 as the cluster HMG-CoA reductase that functions in the mevalonate pathway. Supporting Evidence: file:genes/EMENI/AN1593/AN1593-uniprot.txt Reaction=(R)-mevalonate + 2 NADP(+) + CoA = (3S)-3-hydroxy-3- methylglutaryl-CoA + 2 NADPH + 2 H(+) PMID:22506079 Based on the data presented here, we suggest a model for ent-pimara-8(14),15-diene biosynthesis in Aspergillus nidulans. Specifically, HMG-CoA reductase (AN1593.4) functions in the mevalonate pathway, which produces isoprenoid precursors. |
| GO:0005778 peroxisomal membrane | IBA GO_REF:0000033 | REMOVE | Summary: IBA peroxisomal membrane from PAINT node PTN000060347. Over-propagated. Reason: PTN000060347 is a broad eukaryotic node that is too deep for the peroxisomal-membrane assertion. The PTHR10572 family review already classifies this node as needing pruning because fungal HMG-CoA reductases are not peroxisomal; AN1593 is a short secondary-metabolite-cluster HMGR that lacks the canonical sterol-sensing membrane domain and has no peroxisomal evidence. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH LINEAGE OR TAXON MISMATCH Sources checked: PANTHER:PTN000060347 SUPPORTS SOURCE BUT NOT TARGET The node also carries a sound ER-membrane term for long canonical HMGRs, but the peroxisomal placement is too broad and should be pruned from fungal descendants. Supporting Evidence: file:interpro/panther/PTHR10572/PTHR10572-paint.tsv PTHR10572 PTN000060347 GO:0005778 C IBD false file:genes/EMENI/AN1593/AN1593-uniprot.txt CHAIN 1..416 |
| GO:0005789 endoplasmic reticulum membrane | IBA GO_REF:0000033 | REMOVE | Summary: IBA ER membrane from PAINT node PTN000060347. Over-propagated to the short, catalytic-domain-only pimaradiene-cluster paralog. Reason: ER membrane localization is sound for the long housekeeping HMG-CoA reductases reviewed in PTHR10572, but PTN000060347 also reaches AN1593, a cluster-specific 416-residue HMGR that lacks the N-terminal sterol-sensing membrane domain. UniProt's predicted single-pass segment overlaps the catalytic fold near the proton-donor active-site residue, so there is no reliable membrane localization evidence for AN1593. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000060347 SUPPORTS SOURCE BUT NOT TARGET The ER membrane node is well supported for long canonical sterol-pathway HMGRs, but AN1593 is a short cluster HMGR without a defensible membrane anchor. Supporting Evidence: file:interpro/panther/PTHR10572/PTHR10572-paint.tsv PTHR10572 PTN000060347 GO:0005789 C IBD false PMID:22506079 We identified putative genes for HMG-CoA reductase and GGPP-synthase (AN1593.4; GenBank accession number CBF85179.1 and AN1592.4; GenBank accession number CBF85177.1). file:genes/EMENI/AN1593/AN1593-uniprot.txt CHAIN 1..416 file:genes/EMENI/AN1593/AN1593-uniprot.txt ACT_SITE 408 FT /note="Proton donor" |
| GO:0006696 ergosterol biosynthetic process | IBA GO_REF:0000033 | REMOVE | Summary: Fungal ergosterol IBA from PTN000832055. Over-propagated from canonical fungal HMGRs to the pimaradiene-cluster paralog. Reason: The fungal PTN000832055 ergosterol node is appropriate for the long housekeeping fungal HMG-CoA reductases, but AN1593 is not that paralog. AN1593 is embedded in the PbcR-activated ent-pimara-8(14),15-diene cluster, and Bromann et al. proposed that this cluster HMG-CoA reductase specifically supplies mevalonate-derived precursors for diterpene secondary metabolism. Propagation Review Root cause: PROPAGATION BAD Failure modes: WRONG ORTHOLOG OR PARALOG FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000832055 SUPPORTS SOURCE BUT NOT TARGET Fungal ergosterol node seeded by the S. cerevisiae housekeeping HMGR paralog; AN1593 is a secondary-metabolite-cluster HMGR instead. Supporting Evidence: file:interpro/panther/PTHR10572/PTHR10572-paint.tsv PTHR10572 PTN000832055 GO:0006696 P IBD false PMID:22506079 However, HMG-CoA reductase and GGPP-synthase identified in this study may specifically provide precursors for the production of ent-pimara-8(14),15-diene. PMID:22506079 Other studies have identified HMG-CoA reductase (AN3817.2) and GGPP-synthase (AN0654.2, AN2407.2 and AN8143.2) homologs that have been linked to terpenoid biosynthesis in Aspergillus nidulans |
| GO:0008299 isoprenoid biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: Isoprenoid biosynthesis inherited from PAINT node PTN000060346. Correct. Reason: PTN000060346 places broad isoprenoid biosynthesis on the HMG-CoA reductase node, and this broad term still covers AN1593: the A. nidulans literature places AN1593.4 in the mevalonate pathway supplying isoprenoid precursors for the diterpene ent-pimara-8(14),15-diene. Supporting Evidence: file:interpro/panther/PTHR10572/PTHR10572-paint.tsv PTHR10572 PTN000060346 GO:0008299 P IBD false PMID:22506079 Based on the data presented here, we suggest a model for ent-pimara-8(14),15-diene biosynthesis in Aspergillus nidulans. Specifically, HMG-CoA reductase (AN1593.4) functions in the mevalonate pathway, which produces isoprenoid precursors. |
| GO:0008299 isoprenoid biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping of eukaryotic HMG-CoA reductases to isoprenoid biosynthesis. Correct. Reason: AN1593 is a fungal HMG-CoA reductase that retains the eukaryotic/archaeal HMG-CoA reductase InterPro signature and is specifically implicated in the mevalonate pathway for isoprenoid precursor production in the pimaradiene biosynthetic cluster. Supporting Evidence: file:genes/EMENI/AN1593/AN1593-uniprot.txt InterPro; IPR004554; HMG_CoA_Rdtase_eu_arc. PMID:22506079 Based on the data presented here, we suggest a model for ent-pimara-8(14),15-diene biosynthesis in Aspergillus nidulans. Specifically, HMG-CoA reductase (AN1593.4) functions in the mevalonate pathway, which produces isoprenoid precursors. |
| GO:0015936 coenzyme A metabolic process | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: Broad InterPro coenzyme A metabolic process mapping from the HMG-CoA reductase domain. Over-annotation. Reason: AN1593 releases CoA as part of the HMG-CoA reductase reaction, but the supported biological role is production of mevalonate-derived isoprenoid precursors for pimaradiene biosynthesis. Annotating the gene product to the whole coenzyme A metabolic process overstates an incidental substrate/product relationship. Supporting Evidence: file:genes/EMENI/AN1593/AN1593-uniprot.txt Reaction=(R)-mevalonate + 2 NADP(+) + CoA = (3S)-3-hydroxy-3- methylglutaryl-CoA + 2 NADPH + 2 H(+) PMID:22506079 Based on the data presented here, we suggest a model for ent-pimara-8(14),15-diene biosynthesis in Aspergillus nidulans. Specifically, HMG-CoA reductase (AN1593.4) functions in the mevalonate pathway, which produces isoprenoid precursors. |
| GO:0016020 membrane | IEA GO_REF:0000044 | REMOVE | Summary: UniProt SubCell mapping to generic membrane, derived from a likely spurious single-pass prediction. Reason: AN1593 is only 416 aa and consists of the class I HMGR catalytic module. UniProt's predicted transmembrane segment lies inside the catalytic domain, eight residues before the proton-donor active-site residue; it is more likely the conserved C-terminal helix of the soluble HMGR fold than a membrane anchor. Supporting Evidence: file:genes/EMENI/AN1593/AN1593-uniprot.txt SUBCELLULAR LOCATION: Membrane {ECO:0000255}; Single-pass membrane file:genes/EMENI/AN1593/AN1593-uniprot.txt CHAIN 1..416 file:genes/EMENI/AN1593/AN1593-uniprot.txt TRANSMEM 380..400 FT /note="Helical" file:genes/EMENI/AN1593/AN1593-uniprot.txt ACT_SITE 408 FT /note="Proton donor" |
| GO:0016616 oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor | IEA GO_REF:0000002 | TOO GENERAL | Summary: Broad HMG-CoA reductase substrate-binding-domain oxidoreductase mapping. Too general. Reason: The oxidoreductase parent is true of AN1593, but the same record already carries the exact NADPH-dependent HMG-CoA reductase activity that describes the relevant redox chemistry. Supporting Evidence: file:genes/EMENI/AN1593/AN1593-uniprot.txt Reaction=(R)-mevalonate + 2 NADP(+) + CoA = (3S)-3-hydroxy-3- methylglutaryl-CoA + 2 NADPH + 2 H(+) |
| GO:0019748 secondary metabolic process | IEP PMID:22506079 Identification and characterization of a novel diterpene gen... | ACCEPT | Summary: AspGD expression evidence from the PbcR-activated pimaradiene cluster. Correct. Reason: Overexpression of the cluster-specific regulator pbcR strongly upregulated AN1593.4 together with the neighboring pimaradiene-cluster genes, and the activated strain produced ent-pimara-8(14),15-diene. The row's acts_upstream_of_or_within qualifier is appropriate because AN1593 itself has not yet been deleted or assayed for a direct flux contribution to the diterpene product. Supporting Evidence: PMID:22506079 The highly upregulated genes were homologous to GGPP synthase; AN1592.4 (307,000-fold), HMG-CoA reductase; AN1593.4 (12,000-fold), diterpene synthase; AN1594.4 (21,700-fold), translation elongation factor |
| GO:0019748 secondary metabolic process | IGC PMID:22506079 Identification and characterization of a novel diterpene gen... | ACCEPT | Summary: AspGD genetic evidence from the PbcR-activated pimaradiene cluster. Correct. Reason: Bromann et al. identified AN1593.4 as part of the eight-gene PbcR-activated pimaradiene biosynthetic cluster and proposed that its HMG-CoA reductase activity supplies mevalonate-pathway precursors for the secondary metabolite ent-pimara-8(14),15-diene. Supporting Evidence: PMID:22506079 Taken together, these data suggest that the predicted diterpene cluster consists of eight adjacent genes on Aspergillus nidulans chromosome VII in the region AN1592.4 to AN1599.4. |
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Download this section (compressed HTML)Q: Is AN1593 an active HMG-CoA reductase in vitro, or has the secondary-metabolite-cluster paralog lost measurable NADPH-dependent HMG-CoA reductase activity?
Suggested experts: Aspergillus secondary-metabolite curators
Q: Is AN1593 a soluble catalytic-domain protein despite UniProt's predicted C-terminal transmembrane helix?
Suggested experts: UniProt fungal protein curators
Q: Does AN1593 specifically supply mevalonate-derived precursor to the pimaradiene cluster in vivo, rather than merely being co-induced with pbcR?
Suggested experts: Aspergillus secondary-metabolite curators
Experiment: Assay purified recombinant AN1593 for NADPH-dependent reduction of HMG-CoA to mevalonate and compare the rate with the housekeeping A. nidulans HMGR.
Experiment: Fractionate pbcR-overexpressing A. nidulans cells expressing epitope-tagged AN1593, and compare soluble and membrane fractions by immunoblot or targeted proteomics to test the predicted single-pass membrane assignment.
Experiment: Delete AN1593 in a pbcR-overexpression background and quantify ent-pimara-8(14),15-diene production by GC/MS to test whether AN1593 contributes precursor flux to the cluster.
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