Saro_0802 encodes NOV1, a bacterial resveratrol-cleaving dioxygenase (stilbene cleavage oxygenase, SCO) of Novosphingobium aromaticivorans. It is a non-heme Fe(II) enzyme of the carotenoid cleavage oxygenase (CCO/RPE65) superfamily that oxidatively cleaves the central interphenyl Calpha-Cbeta double bond of stilbenes into two aromatic aldehydes; it has been structurally characterized in complex with the substrate resveratrol and the product vanillin. NOV1 is a seven-bladed beta-propeller with an iron cofactor coordinated by four histidines, and its mechanism proceeds via a side-on ferric-superoxide that reacts with substrate activated by deprotonation of the 4-hydroxyl (4'-OH), making the 4'-OH catalytically essential; NOV1 cleaves a wide range of 4'-hydroxy stilbene-like compounds. It also converts the lignin-derived phenylpropene isoeugenol to vanillin and is of interest for lignin valorization. Despite automated annotations to the contrary, NOV1 is not a carotenoid cleavage enzyme.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0010436 carotenoid dioxygenase activity | IEA GO_REF:0000118 | REMOVE | Summary: Automated (IEA / TreeGrafter) annotation of carotenoid dioxygenase activity. This is the wrong substrate class: NOV1 is a stilbene cleavage oxygenase that cleaves resveratrol (and other 4'-OH stilbenes) and isoeugenol, demonstrated structurally with resveratrol bound (PMID:27911781). The carotenoid term is a TreeGrafter over-propagation from the mixed-specificity CCO family. Reason: Rule/tree-based over-annotation contradicted by the enzyme's structural and functional characterization as a resveratrol/stilbene dioxygenase. The correct specific term is GO:7770086 (resveratrol dioxygenase activity, RHEA:73735; added go-ontology master Jul 2026); the real activity is already covered generally by GO:0016702. Same substrate-class error as cao-1, here via TreeGrafter (GO_REF:0000118) rather than manual IBA. Supporting Evidence: PMID:27911781 Stilbene cleavage oxygenases (SCOs) cleave the central double PMID:27911781 NOV1 cleaves a wide range of other stilbene-like compounds with a 4'-OH group |
| GO:0016121 carotene catabolic process | IEA GO_REF:0000118 | MODIFY | Summary: Automated (IEA / TreeGrafter) annotation of carotene catabolic process. Wrong substrate class: NOV1 acts in stilbene / lignin-derived compound catabolism, not carotene catabolism. Reason: Replace with GO:0046272 (stilbene catabolic process), matching the demonstrated stilbene-cleavage activity. Same TreeGrafter over-propagation as the carotenoid MF term. Proposed replacements: stilbene catabolic process Supporting Evidence: PMID:27911781 Stilbene cleavage oxygenases (SCOs) cleave the central double |
| GO:0016702 oxidoreductase activity, acting on single donors with incorporation of molecular oxygen, incorporation of two atoms of oxygen | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based (IEA) dioxygenase MF term (incorporation of two oxygen atoms). Correct and consistent with the demonstrated stilbene dioxygenase activity of NOV1. Reason: Accurate general dioxygenase MF; the specific activity (resveratrol/stilbene cleavage) sits under this term. Supporting Evidence: PMID:27911781 an iron cofactor coordinated by four histidines |
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Download this section (compressed HTML)Q: The carotenoid dioxygenase activity/process annotations on NOV1 come from the TreeGrafter rule (GO_REF:0000118); should this rule be corrected so it does not assign carotenoid terms to the stilbene-cleaving (SCO) branch of the CCO family?
Experiment: Comparative substrate-panel + structural analysis of NOV1 versus CAO-1 to test whether the wider 4'-hydroxy-stilbene tolerance of NOV1 reflects a more open binding cleft than CAO-1's two-anchor (4'-OH -> Tyr/Lys; 3/5-OH -> Glu) pocket.
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