Saro_2809

UniProt ID: Q2G4H8
Organism: Novosphingobium aromaticivorans (strain ATCC 700278 / DSM 12444 / CCUG 56034 / CIP 105152 / NBRC 16084 / F199)
Review Status: IN PROGRESS
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Gene Description

Saro_2809 encodes NOV2, the second stilbene cleavage oxygenase (SCO) of Novosphingobium aromaticivorans and a paralog of NOV1 (Saro_0802). It is a non-heme Fe(II) enzyme of the carotenoid cleavage oxygenase (CCO/RPE65) superfamily that oxidatively cleaves the interphenyl Calpha-Cbeta double bond of stilbenoids; NOV2 was characterized biochemically and spectroscopically alongside Neurospora CAO-1, using resveratrol and piceatannol as substrates. Like the other SCOs, and despite automated annotations to the contrary, NOV2 is a stilbenoid cleaver, not a carotenoid enzyme.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0010436 carotenoid dioxygenase activity
IEA
GO_REF:0000118 		REMOVE
Summary: Automated (IEA / TreeGrafter) carotenoid dioxygenase activity. NOV2 is a stilbene cleavage oxygenase assayed with resveratrol and piceatannol (PMID:28493664), not a carotenoid enzyme; the carotenoid term is a TreeGrafter over-propagation from the mixed CCO family.
Reason: Rule/tree-based over-annotation of the wrong substrate class. Correct specific term is GO:7770086 (resveratrol dioxygenase activity; go-ontology PR #32332, merged 2026-07-17, live in QuickGO); the general activity is covered by GO:0016702. Same error as NOV1 and cao-1.
Supporting Evidence:
PMID:28493664
resveratrol and piceatannol for NOV2 and CAO1
GO:0016121 carotene catabolic process
IEA
GO_REF:0000118 		MODIFY
Summary: Automated (IEA / TreeGrafter) carotene catabolic process. Wrong substrate class; NOV2 acts in stilbene/lignin-derived compound catabolism.
Reason: Replace with GO:0046272 (stilbene catabolic process). Same TreeGrafter over-propagation as the carotenoid MF term.
Proposed replacements: stilbene catabolic process
Supporting Evidence:
PMID:28493664
resveratrol and piceatannol for NOV2 and CAO1
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; correct general parent for the stilbenoid-cleavage activity of NOV2.
Reason: Accurate general dioxygenase MF; consistent with the demonstrated stilbenoid cleavage.

Core Functions

Non-heme Fe(II) stilbene cleavage dioxygenase (SCO) that cleaves the interphenyl Calpha-Cbeta double bond of stilbenoids (resveratrol, piceatannol) into aromatic aldehydes. GO:0016702 is the validated MF term available in the ontology snapshot this repo validates against; the specific term is GO:7770086 (resveratrol dioxygenase activity, RHEA:73735; go-ontology PR #32332, merged 2026-07-17).

Molecular Function:
oxidoreductase activity, acting on single donors with incorporation of molecular oxygen, incorporation of two atoms of oxygen
Directly Involved In:
stilbene catabolic process
Supporting Evidence:

References

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Suggested Questions for Experts

Q: NOV2's carotenoid annotations come from TreeGrafter (GO_REF:0000118); should the rule be corrected so it does not assign carotenoid terms to the stilbene-cleaving (SCO) branch of the CCO family?

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