CYP79F2 (hexahomomethionine N-hydroxylase) is an endoplasmic reticulum membrane-anchored cytochrome P450 monooxygenase that catalyzes the aldoxime-forming entry step of core structure formation for long-chain methionine-derived (aliphatic) glucosinolates. Using O2 and electrons from NADPH-cytochrome P450 reductase it converts the long-chain methionine homologues penta- and hexahomomethionine to 8-methylthiooctanaldoxime and 9-methylthiononanaldoxime (EC 1.14.14.42). It arose by tandem duplication with CYP79F1 (about 89% amino-acid identity) but, unlike CYP79F1, does not accept short-chain homologues, so it cannot substitute for CYP79F1 in short-chain glucosinolate synthesis. CYP79F2 is expressed mainly in hypocotyl and root vasculature and is induced by methyl jasmonate. Loss of CYP79F2 substantially reduces long-chain aliphatic glucosinolates without affecting short-chain ones, and cyp79f1 cyp79f2 double mutants lack aliphatic glucosinolates entirely; the mild lateral-root phenotype of cyp79f2 mutants is regarded as a secondary consequence of the metabolic block.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004497 monooxygenase activity | IEA GO_REF:0000002 | MODIFY | Summary: The demonstrated activity is homomethionine N-monooxygenase. Reason: Recombinant-enzyme substrate/product measurements support GO:0120526, already asserted in this review. Use the same target-specific replacement across evidence types. Electron delivery is through the P450 reductase/flavoprotein system; correcting the direct NAD(P)H-donor wording is a reaction-class correction where applicable. Proposed replacements: homomethionine N-monooxygenase activity Supporting Evidence: |
| GO:0005506 iron ion binding | IEA GO_REF:0000002 | ACCEPT | Summary: Heme iron is the catalytic cofactor of this P450 monooxygenase. Reason: Heme/iron binding supports the established P450 oxygenation chemistry. It is an intrinsic catalytic feature, not a peripheral process or an additional independent core activity. Supporting Evidence: |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of ER localization for plant P450s; CYP79F2 (AT1G16400) is itself an experimental donor, as expected. Consistent with GFP-fusion evidence. Reason: ER localization is experimentally confirmed for the CYP79F2 N-terminal anchor. Supporting Evidence: PMID:11226190 Comparison of the fluorescence patterns between the controls and the fusion proteins revealed that the GFP fusions of CYP79F1 and CYP79F2 were both located in the ER |
| GO:0005783 endoplasmic reticulum | IDA PMID:11226190 Bus, a bushy Arabidopsis CYP79F1 knockout mutant with abolis... | ACCEPT | Summary: The first 62 residues of CYP79F2 fused to GFP co-localized with an ER-targeted GFP control, showing ER targeting. Reason: Direct experimental localization consistent with microsomal P450 topology. Supporting Evidence: PMID:11226190 The first 62 amino acids of either CYP79F1 or CYP79F2 (named N-CYP79F1 and N-CYP79F2), which include the motifs mentioned above ( Figure 3 ), were fused to green fluorescent protein (GFP). PMID:11226190 Comparison of the fluorescence patterns between the controls and the fusion proteins revealed that the GFP fusions of CYP79F1 and CYP79F2 were both located in the ER |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (ER membrane, single-pass). Most precise location for the enzyme. Reason: Correct and appropriately specific location for a microsomal P450. Supporting Evidence: PMID:11226190 a stretch of hydrophobic amino acids constituting the transmembrane helix, which anchors the protein in the ER |
| GO:0009507 chloroplast | ISM GO_REF:0000122 | REMOVE | Summary: AtSubP sequence-based prediction, contradicted by experimentally demonstrated ER targeting of the CYP79F2 N-terminus (an ER signal-anchor, not a transit peptide). Reason: Computational prediction contradicted by direct localization evidence. Supporting Evidence: PMID:11226190 Comparison of the fluorescence patterns between the controls and the fusion proteins revealed that the GFP fusions of CYP79F1 and CYP79F2 were both located in the ER |
| GO:0009625 response to insect | IEP PMID:40546745 Impact of Lepidopteran Oral Secretions on the Transcriptome ... | KEEP AS NON CORE | Summary: Caterpillar oral secretions suppressed aliphatic glucosinolate biosynthetic gene expression; CYP79F2 was among the qPCR-validated genes. Expression response only. Reason: Transcriptional regulation in response to insect elicitors is a regulatory context of a biosynthetic enzyme, not evidence that CYP79F2 performs a response process. Supporting Evidence: PMID:40546745 Expression level of MYB28 (At5g61420), CYP79F1 (At1g16410), and CYP79F2 (At1g16400) 3 h after treatment PMID:40546745 Strikingly, OS of both caterpillars suppressed the basal expression of MYC4, MYB28, and MYB29 and most genes responsible for aliphatic GS biosynthesis (Figure 6A), three of which were further validated by qPCR (Figure 6B). |
| GO:0016020 membrane | IBA GO_REF:0000033 | MODIFY | Summary: CYP79F is anchored in the endoplasmic reticulum membrane. Reason: Refine generic membrane to the supported ER membrane location already present in this review; GFP-fusion localization and microsomal P450 topology support this assignment. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN001210282 UNRESOLVED Proximate PAINT node traced from the original annotation. Its full ancestral assertion history has not been reconstructed in this audit; the target-specific assessment is grounded in the primary evidence explained in review.reason, not donor counts or self-inclusion. Proposed replacements: endoplasmic reticulum membrane Supporting Evidence: |
| GO:0016705 oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen | IEA GO_REF:0000002 | MODIFY | Summary: The demonstrated activity is homomethionine N-monooxygenase. Reason: Recombinant-enzyme substrate/product measurements support GO:0120526, already asserted in this review. Use the same target-specific replacement across evidence types. Electron delivery is through the P450 reductase/flavoprotein system; correcting the direct NAD(P)H-donor wording is a reaction-class correction where applicable. Proposed replacements: homomethionine N-monooxygenase activity Supporting Evidence: |
| GO:0016709 oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen, NAD(P)H as one donor, and incorporation of one atom of oxygen | IBA GO_REF:0000033 | MODIFY | Summary: The demonstrated activity is homomethionine N-monooxygenase. Reason: Recombinant-enzyme substrate/product measurements support GO:0120526, already asserted in this review. Use the same target-specific replacement across evidence types. Electron delivery is through the P450 reductase/flavoprotein system; correcting the direct NAD(P)H-donor wording is a reaction-class correction where applicable. Propagation Review Root cause: TERM SCOPING PROBLEM Sources checked: PANTHER:PTN001210282 · PTN001210282 SUPPORTS TRANSFER The P450 monooxygenase function at this node is sound and CYP79F2 is inside the clade; only the electron-donor branch of the asserted term is mis-scoped for microsomal P450s. Proposed replacements: homomethionine N-monooxygenase activity Supporting Evidence: |
| GO:0016709 oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen, NAD(P)H as one donor, and incorporation of one atom of oxygen | IDA PMID:12609033 CYP79F1 and CYP79F2 have distinct functions in the biosynthe... | MODIFY | Summary: The demonstrated activity is homomethionine N-monooxygenase. Reason: Recombinant-enzyme substrate/product measurements support GO:0120526, already asserted in this review. Use the same target-specific replacement across evidence types. Electron delivery is through the P450 reductase/flavoprotein system; correcting the direct NAD(P)H-donor wording is a reaction-class correction where applicable. Proposed replacements: homomethionine N-monooxygenase activity Supporting Evidence: |
| GO:0019761 glucosinolate biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT node for the CYP79F clade (CYP79F1 and CYP79F2 as donors). CYP79F2 catalyzes the aldoxime-forming step for long-chain aliphatic glucosinolates. Reason: Core process with direct biochemical and genetic support on the target. Supporting Evidence: PMID:12609033 The level of long-chain aliphatic glucosinolates in a transposon-tagged CYP79F2 knockout mutant is substantially reduced, whereas the level of short-chain aliphatic glucosinolates is not affected. |
| GO:0019761 glucosinolate biosynthetic process | IMP PMID:12609033 CYP79F1 and CYP79F2 have distinct functions in the biosynthe... | ACCEPT | Summary: A transposon-tagged cyp79f2 knockout has substantially reduced long-chain aliphatic glucosinolates; combined with enzyme assays this shows CYP79F2 performs a step of glucosinolate biosynthesis. Reason: Mutant phenotype plus demonstrated catalytic activity establish direct participation. Supporting Evidence: PMID:12609033 The level of long-chain aliphatic glucosinolates in a transposon-tagged CYP79F2 knockout mutant is substantially reduced, whereas the level of short-chain aliphatic glucosinolates is not affected. PMID:15194821 Our analysis shows that aliphatic glucosinolate biosynthesis is completely abolished in the double-knockout plants, providing genetic proof for the proposed biochemical functions of these genes. |
| GO:0020037 heme binding | IEA GO_REF:0000002 | ACCEPT | Summary: Heme iron is the catalytic cofactor of this P450 monooxygenase. Reason: Heme/iron binding supports the established P450 oxygenation chemistry. It is an intrinsic catalytic feature, not a peripheral process or an additional independent core activity. Supporting Evidence: |
| GO:0120526 homomethionine N-monooxygenase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Rhea/EC-based mapping of the experimentally characterized CYP79F2 reactions (penta- and hexahomomethionine to their aldoximes). This is the core molecular function. Reason: Directly supported by recombinant-enzyme assays with defined substrates. Supporting Evidence: PMID:12609033 In contrast, CYP79F2 exclusively metabolizes long-chain elongated penta- and hexahomomethionines. |
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Download this section (compressed HTML)Q: Which residues restrict CYP79F2 to long-chain methionine homologues, and is the short-chain activity of CYP79F1 the derived or ancestral state in the Brassicaceae CYP79F duplication?
Q: Does the root-biased expression of CYP79F2 reflect a specific defensive role of long-chain aliphatic glucosinolates in roots?
Experiment: Compare root glucosinolate profiles and performance of root-feeding insects or root pathogens on cyp79f2 single, cyp79f1 single and double mutants.
Hypothesis: Long-chain aliphatic glucosinolates made by CYP79F2 contribute to root defence against soil herbivores or pathogens.
Type: genetic and bioassay
Experiment: Chimeras and point mutants between CYP79F1 and CYP79F2 assayed on mono- to hexahomomethionine in yeast microsomes.
Hypothesis: CYP79F2 substrate specificity is set by a small number of residues.
Type: site-directed mutagenesis and enzyme kinetics
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