Carboxyspermidine decarboxylase (CasDC), a member of the NspC branch of the PLP-dependent group IV decarboxylase family. BT_0674 catalyzes the terminal conversion of carboxyspermidine to spermidine in Bacteroides thetaiotaomicron. Deletion depletes spermidine and decarboxylase activity and impairs growth in polyamine-free medium; complementation restores these phenotypes. A physiological norspermidine pathway is not established.
Definition: Catalysis of the decarboxylation of carboxyspermidine to spermidine and carbon dioxide.
Justification: The target evidence supports carboxyspermidine decarboxylation. The dual-substrate family label does not establish carboxynorspermidine turnover by BT_0674, so this proposal is restricted to the supported reaction; neither absence of that alternative activity nor its native use is asserted.
Parent term: carboxy-lyase activity
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad catalytic term can be refined to the supported carboxyspermidine decarboxylation activity. Reason: The abstract reports loss and restoration of decarboxylase activity with deletion/complementation, and the accessible primary Figure 1 identifies CASDC as BT_0674. Refine to a carboxyspermidine-only decarboxylase proposal; activity on carboxynorspermidine has not been verified for this target. A specific GO term was not found in current QuickGO searches. Proposed replacements: carboxyspermidine decarboxylase activity Supporting Evidence: PMID:27118128 The complemented ฮcasdc strain restored the spermidine biosynthetic ability, decarboxylase activity, and growth. file:BACTN/BT_0674/BT_0674-uniprot.txt PANTHER; PTHR43727:SF1; CARBOXYNORSPERMIDINE_CARBOXYSPERMIDINE DECARBOXYLASE |
| GO:0008836 diaminopimelate decarboxylase activity | IBA GO_REF:0000033 | REMOVE | Summary: LysA function has been propagated into the divergent NspC/CasDC branch. Reason: The family review scopes these IBD claims at PTN000159906 to LysA SF2 and calls for pruning SF1. BT_0674 is an SF1 member with target-species carboxyspermidine decarboxylase genetics/activity, rather than a diaminopimelate-processing lysine-biosynthetic enzyme. This challenges branch scope, not donor count. No IRD/IKR loss is present on this lineage in the checked PAINT snapshot; no direct BT_0674 negative diaminopimelate assay is claimed. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000159906 SUPPORTS SOURCE BUT NOT TARGET The family IBD is grounded in genuine LysA descendants, but the PTHR43727 family review excludes the function from divergent NspC SF1 members such as BT_0674. Supporting Evidence: file:BACTN/BT_0674/BT_0674-uniprot.txt PANTHER; PTHR43727:SF1; CARBOXYNORSPERMIDINE_CARBOXYSPERMIDINE DECARBOXYLASE PMID:27118128 The complemented ฮcasdc strain restored the spermidine biosynthetic ability, decarboxylase activity, and growth. |
| GO:0009085 L-lysine biosynthetic process | IBA GO_REF:0000033 | REMOVE | Summary: LysA function has been propagated into the divergent NspC/CasDC branch. Reason: The family review scopes these IBD claims at PTN000159906 to LysA SF2 and calls for pruning SF1. BT_0674 is an SF1 member with target-species carboxyspermidine decarboxylase genetics/activity, rather than a diaminopimelate-processing lysine-biosynthetic enzyme. This challenges branch scope, not donor count. No IRD/IKR loss is present on this lineage in the checked PAINT snapshot; no direct BT_0674 negative diaminopimelate assay is claimed. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000159906 SUPPORTS SOURCE BUT NOT TARGET The family IBD is grounded in genuine LysA descendants, but the PTHR43727 family review excludes the function from divergent NspC SF1 members such as BT_0674. Supporting Evidence: file:BACTN/BT_0674/BT_0674-uniprot.txt PANTHER; PTHR43727:SF1; CARBOXYNORSPERMIDINE_CARBOXYSPERMIDINE DECARBOXYLASE PMID:27118128 The complemented ฮcasdc strain restored the spermidine biosynthetic ability, decarboxylase activity, and growth. |
| GO:0016831 carboxy-lyase activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad catalytic term can be refined to the supported carboxyspermidine decarboxylation activity. Reason: The abstract reports loss and restoration of decarboxylase activity with deletion/complementation, and the accessible primary Figure 1 identifies CASDC as BT_0674. Refine to a carboxyspermidine-only decarboxylase proposal; activity on carboxynorspermidine has not been verified for this target. A specific GO term was not found in current QuickGO searches. Proposed replacements: carboxyspermidine decarboxylase activity Supporting Evidence: PMID:27118128 The complemented ฮcasdc strain restored the spermidine biosynthetic ability, decarboxylase activity, and growth. file:BACTN/BT_0674/BT_0674-uniprot.txt PANTHER; PTHR43727:SF1; CARBOXYNORSPERMIDINE_CARBOXYSPERMIDINE DECARBOXYLASE |
| GO:0045312 nor-spermidine biosynthetic process | IEA GO_REF:0000002 | MODIFY | Summary: The established native product is spermidine; refine the pathway assignment accordingly. Reason: The generic NspC-family mapping to norspermidine does not establish endogenous norspermidine synthesis. Target-species deletion/complementation and decarboxylase activity support the carboxyspermidine-to-spermidine step. This is a lateral product/pathway correction, not an assertion that purified BT_0674 cannot accept carboxynorspermidine. Proposed replacements: spermidine biosynthetic process Supporting Evidence: PMID:27118128 The complemented ฮcasdc strain restored the spermidine biosynthetic ability, decarboxylase activity, and growth. |
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Gap: The full substrate selectivity of BT_0674 is unresolved.
OPEN BIOLOGY
What is known: The accessible primary abstract establishes carboxyspermidine-related activity and native spermidine synthesis; the full paper was inaccessible, and no exact kinetic constants or alternative-substrate exclusions are asserted.
Significance: Determines physiological substrate use and the correct pathway assignment.
What would resolve it: Obtain full text and compare purified BT_0674 with carboxyspermidine, carboxynorspermidine and CAPA.
Provenance (the field's own admissions):
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