tetX encodes an FAD-dependent tetracycline monooxygenase from Sphingobacterium sp. PM2-P1-29. The enzyme uses NADPH and oxygen to hydroxylate tetracycline at carbon 11a, initiating tetracycline breakdown and inactivation. This antibiotic-destruction activity explains the tetracycline resistance phenotype of the source organism and of heterologous hosts expressing tetX.
Definition: Catalysis of the NADPH- and oxygen-dependent hydroxylation of tetracycline at carbon 11a, producing 11a-hydroxytetracycline and initiating tetracycline antibiotic inactivation.
Justification: GO has only the broad monooxygenase activity term for TetX, but TetX-family AMR determinants have a substrate- and position-specific antibiotic destruction activity supported by Rhea/EC information and experimental TetX literature.
Parent term: monooxygenase activity
Mappings:
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000166 nucleotide binding | IEA GO_REF:0000104 | KEEP AS NON CORE | Summary: Broad cofactor-binding annotation. TetX binds flavin/nucleotide cofactors, but the informative function is FAD-dependent tetracycline monooxygenase activity. Reason: The annotation is compatible with the FAD/NADPH-dependent enzyme record, but it is too general to represent the core biological activity. Supporting Evidence: file:genes/SPHSM/tetX/tetX-uniprot.txt Name=FAD |
| GO:0004497 monooxygenase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct core molecular function, but much broader than the TetX-specific tetracycline C11a monooxygenase/destructase activity. Reason: UniProt and the cached TetX papers directly support a monooxygenase that acts on tetracycline. GO currently has only the broader monooxygenase term; a specific TetX/tetracycline 11a-monooxygenase term is proposed below. Supporting Evidence: file:genes/SPHSM/tetX/tetX-uniprot.txt An FAD-requiring monooxygenase active on some tetracycline PMID:19187139 tet(X) encodes for a NADP-dependent monooxygenase that requires oxygen to degrade tetracycline PMID:26038239 TetX is a flavin-dependent monooxygenase. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: Cytoplasmic localization is consistent with a soluble bacterial antibiotic-inactivation enzyme. Reason: The UniProt record carries the cytoplasm GO annotation and does not indicate secretion or membrane localization. Supporting Evidence: file:genes/SPHSM/tetX/tetX-uniprot.txt DR GO; GO:0005737; C:cytoplasm |
| GO:0046677 response to antibiotic | IEA GO_REF:0000002 | ACCEPT | Summary: Correct high-level biological process for a tetracycline-inactivation resistance enzyme. Reason: The response/resistance annotation is biologically sound, but the core value for this review is the missing precise molecular-function term. Supporting Evidence: file:genes/SPHSM/tetX/tetX-uniprot.txt DR CARD; ARO:3000205; tet(X); ARO:0001004; antibiotic inactivation. PMID:26038239 It has been reported to inactivate all tested tetracyclines. |
| GO:0071949 FAD binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct cofactor-binding annotation for a flavin-dependent monooxygenase. Reason: FAD binding is mechanistically relevant but secondary to the catalytic antibiotic-inactivation activity. Supporting Evidence: file:genes/SPHSM/tetX/tetX-uniprot.txt Name=FAD |
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Download this section (compressed HTML)Q: Should GO add a TetX-family tetracycline 11a-monooxygenase activity term distinct from generic monooxygenase activity?
Experiment: Assay purified TetX against tetracycline-class substrates and identify 11a-hydroxylated products by LC-MS to delimit substrate scope for the GO term.
Type: in vitro enzyme assay
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