stemphyloxin I

CHEBI:145070 EXACT SEEDED

What these status tags mean

Curation status describes a workflow state. SEEDED means the record entered through the source-seeding workflow; it does not imply that no later curation occurred. PROPOSED marks an addition awaiting review; REVIEWED records curator sign-off on identity, structure, filing class and producer claims; DEPRECATED retains a superseded or out-of-scope record. These are workflow decisions, not independently verified human review. Agent-assisted contributions may appear in the record history.

Grounding describes the identifier mapping: EXACT uses an ontology identity asserted by the source; MINTED keeps a local identifier when no defensible ontology identity is available; REVIEW_NEEDED flags an exact structure whose ontology identity needs adjudication. The grounding note retains any unresolved alternatives. These tags do not establish the strength of producer or activity evidence.

An octahydronaphthalene that is 2,4,5,7-tetramethyloctahydronaphthalen-1(2H)-one which is substituted by hydroxy groups at positions 2 and 7, a (2R)-1-hydroxybutan-2-yl group at position 3, and a (2Z)-3-hydroxyprop-2-enoyl group at position 4 (the 2S,3R,4R,4aS,5R,7R,8aS stereoisomer). Isolated from the endophytic fungus Stemphylium botryosum, it is the causal agent of leaf spot and foliage blight disease in tomatoes. Its phytotoxcity is at least 200 times greater than that of stemphyloxin II. It shows high affinity for Fe3+ (but not Fe2+) ions.

Structure

Standard InChIKey	YRECHDUAXCBBOZ-HOCCXODSSA-N
SMILES	[H][C@]12[C@@](C[C@](C)(O)C[C@H]2C)([H])C([C@@](C)(O)[C@]([H])([C@H](CO)CC)[C@]1(C)C(/C=C\O)=O)=O
Stereochemistry	fully defined

Filing pathway

Polyketides — computed by NPClassifier npclassifier.gnps2.org@2026-09-07, which is why it is pinned rather than recomputed. The gene cluster's asserted class is pks, from MIBiG.

Producer organisms 1

A claim that this taxon makes the compound. The basis says what the evidence addressed — a knockout and a database assertion are not the same claim.

Taxon	Basis	Cluster	Evidence
Parastagonospora nodorum SN15 NCBITaxon:321614	SOURCE_ASSERTION	mibig:BGC0002165	PMID:31553484

Occurrences 3

Somebody found the compound in this organism and cited it. That is not a claim that the organism makes it, and nothing here promotes one to the other.

Taxon	Source	Reference
Stemphylium botryosum NCBITaxon:120510	LOTUS	DOI:10.1016/S0031-9422(00)80518-X
Stemphylium botryosum NCBITaxon:120510	LOTUS	DOI:10.1126/SCIENCE.220.4601.1065
Stemphylium botryosum NCBITaxon:120510	CHEBI	PMID:16662165

Biosynthetic gene clusters 1

Accession	Host	Locus evidence	Genome
mibig:BGC0002165	Parastagonospora nodorum SN15 NCBITaxon:321614	CLUSTER_UNSTATED	genbank:CH445335.1

A locus claim and a taxon claim are different questions. Heterologous expression settles the first and leaves the second where the isolation report left it.

Biosynthesis curated

Written by a curator with claim-level evidence on each step; not derived from a source. This is what the rest of the record exists to support.

Step	Enzyme	Reaction	Substrate → product	Evidence
1	SthD cytochrome P450 monooxygenase UniProtKB:Q0UK51	RHEA:62712	CHEBI:145053 → CHEBI:145070	DOI:10.1002/chem.201904360

Step 1: SthD hydroxylates betaenone C at C-15 to afford compound 7 / stemphyloxin I; this single curated tailoring step leaves upstream assembly from dehydroprobetaenone I to betaenone C unexpanded.

Mechanism & Biosynthesis Overview

Causal graph — biosynthesis 3 nodes, 2 edges

Parastagonospora nodorum SN15 SthD C-15-hydroxylates betaenone C to form stemphyloxin I.

Subject	Predicate	Object	Notes	Evidence
betaenone C	is hydroxylated by	SthD	SthD uses NADPH and O2 in the RHEA:62712 C-15 hydroxylation of betaenone C.	DOI:10.1002/chem.201904360 https://mibig.secondarymetabolites.org/repository/BGC0002165.3/BGC0002165.gbk https://www.uniprot.org/uniprotkb/Q0UK51 https://www.rhea-db.org/rhea/62712 reference DOI:10.1002/chem.201904360 evidence type PRIMARY_EXPERIMENT notes Li et al. activated the Parastagonospora nodorum SN15 stemphyloxin II cluster and used heterologous reconstruction to assign SthD C-15 hydroxylation of betaenone C to compound 7 / stemphyloxin I. reference https://mibig.secondarymetabolites.org/repository/BGC0002165.3/BGC0002165.gbk evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes MIBiG BGC0002165.3 places SNOG_07863 on GenBank CH445335.1 with protein_id EAT85329.1 in the Parastagonospora nodorum SN15 stemphyloxin II BGC. reference https://www.uniprot.org/uniprotkb/Q0UK51 evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes Reviewed UniProtKB:Q0UK51 is the 475 aa Phaeosphaeria nodorum SN15, synonymous with Parastagonospora nodorum SN15, cytochrome P450 monooxygenase SthD / SNOG_07863 gene product; it cross-references EMBL CH445335 protein EAT85329.1 and annotates catalytic activity RHEA:62712 / RHEA:62713. reference https://www.rhea-db.org/rhea/62712 evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes RHEA:62712 is the betaenone C plus NADPH plus O2 plus H(+) to stemphyloxin I plus NADP(+) plus H2O reaction; Rhea maps the master reaction to UniProtKB:Q0UK51 in Swiss-Prot.
SthD	forms	stemphyloxin I	SthD is the SNOG_07863 cytochrome P450 monooxygenase in the BGC0002165 Parastagonospora nodorum SN15 cluster.	DOI:10.1002/chem.201904360 https://mibig.secondarymetabolites.org/repository/BGC0002165.3/BGC0002165.gbk https://www.uniprot.org/uniprotkb/Q0UK51 https://www.rhea-db.org/rhea/62712 reference DOI:10.1002/chem.201904360 evidence type PRIMARY_EXPERIMENT notes Li et al. activated the Parastagonospora nodorum SN15 stemphyloxin II cluster and used heterologous reconstruction to assign SthD C-15 hydroxylation of betaenone C to compound 7 / stemphyloxin I. reference https://mibig.secondarymetabolites.org/repository/BGC0002165.3/BGC0002165.gbk evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes MIBiG BGC0002165.3 places SNOG_07863 on GenBank CH445335.1 with protein_id EAT85329.1 in the Parastagonospora nodorum SN15 stemphyloxin II BGC. reference https://www.uniprot.org/uniprotkb/Q0UK51 evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes Reviewed UniProtKB:Q0UK51 is the 475 aa Phaeosphaeria nodorum SN15, synonymous with Parastagonospora nodorum SN15, cytochrome P450 monooxygenase SthD / SNOG_07863 gene product; it cross-references EMBL CH445335 protein EAT85329.1 and annotates catalytic activity RHEA:62712 / RHEA:62713. reference https://www.rhea-db.org/rhea/62712 evidence type DATABASE_ASSERTION retrieved on 2026-09-30 notes RHEA:62712 is the betaenone C plus NADPH plus O2 plus H(+) to stemphyloxin I plus NADP(+) plus H2O reaction; Rhea maps the master reaction to UniProtKB:Q0UK51 in Swiss-Prot.

Every edge carries its own citation; an uncited edge is refused by the corpus tests.

Explore across X-Mech

AntibioticMech (stemphyloxin I) ↗ MediaIngredientMech (CHEBI:145070) ↗ TaxonMech: Parastagonospora nodorum SN15 (NCBITaxon:321614) ↗ PathwayMech (mibig:BGC0002165) ↗

Open questions 1

name-disagreement — ChEBI calls this structure 'stemphyloxin I' and MIBiG calls it 'compound 7'. They share a Standard InChIKey, so if the names denote different compounds then one upstream record has the wrong structure. Check which.

Provenance

Source concept	Source	Version
BGC0002165	MIBIG	3
CHEBI:145070	CHEBI	3-star

This page is generated from data/natural_products/polyketides/stemphyloxin-i.yaml, which is generated from the committed inventories. Neither is edited by hand.