sad-I (PP_2488) encodes a predicted succinate-semialdehyde dehydrogenase of the GabD1/Sad aldehyde-dehydrogenase family in Pseudomonas putida KT2440. It is expected to oxidize succinate semialdehyde to succinate with a nicotinamide nucleotide acceptor. Its measured NAD versus NADP preference and physiological substrate regime remain unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IEA GO_REF:0000002 | MODIFY | Summary: The aldehyde-dehydrogenase substrate class is resolved to succinate-semialdehyde oxidation without selecting one nicotinamide cofactor. Reason: PANTHER, the SSADH FunFam and GabD1-like CDD classification agree on succinate-semialdehyde oxidation. They are computational classifications, not independent target enzyme assays. For Sad-I, the NADP-named PTHR43217:SF2 subgroup is a substantive competing cofactor classification against the NAD-dependent FunFam. Neither is dismissed as experimental or privileged merely because it matches GOA. This is a substrate-specific semantic refinement to GO:0009013; live QuickGO does not currently place GO:0009013 below GO:0004030, so no is_a relationship between that pair is claimed. Neither the P. putida isoenzymes in PMID:3355840 nor Salmonella YneI in PMID:23229889 establishes a locus-specific 4HB, GABA or putrescine pathway. Proposed replacements: succinate-semialdehyde dehydrogenase [NAD(P)+] activity Supporting Evidence: file:PSEPK/sad-I/sad-I-uniprot.txt FunFam; 3.40.605.10:FF:000012; NAD-dependent succinate-semialdehyde dehydrogenase; 1. file:PSEPK/sad-I/sad-I-uniprot.txt CDD; cd07100; ALDH_SSADH1_GabD1; 1. file:PSEPK/sad-I/sad-I-uniprot.txt PANTHER; PTHR43217:SF2; SUCCINATE-SEMIALDEHYDE DEHYDROGENASE [NADP(+)]; 1. |
| GO:0004777 succinate-semialdehyde dehydrogenase (NAD+) activity | IEA GO_REF:0000120 | ACCEPT | Summary: PP_2488 retains a qualified NAD-capacity inference; its measured acceptor preference is unresolved. Reason: The exact Q88K05 NAD-dependent SSADH FunFam supplies positive functional-family evidence for NAD capacity. For Sad-I, the NADP-named PTHR43217:SF2 subgroup is a substantive competing cofactor classification against the NAD-dependent FunFam. Neither is dismissed as experimental or privileged merely because it matches GOA. Retention of GO:0004777 is therefore a contested family-level inference, not a resolved cofactor assignment. The live GO definition describes NAD-supported catalysis and does not assert exclusive NAD use or absence of NADP activity. PMID:3355840 separates P. putida NAD-preferring and NADP-dependent isoenzymes but does not map either to this locus; Salmonella YneI promiscuity in PMID:23229889 is contextual, not a target assay. The ARBA-only NADP keyword is not used as independent evidence in either direction. The core and broad-term refinements retain cofactor-general SSADH chemistry rather than using this inference to settle physiological acceptor choice. Supporting Evidence: file:PSEPK/sad-I/sad-I-uniprot.txt FunFam; 3.40.605.10:FF:000012; NAD-dependent succinate-semialdehyde dehydrogenase; 1. file:PSEPK/sad-I/sad-I-uniprot.txt CDD; cd07100; ALDH_SSADH1_GabD1; 1. file:PSEPK/sad-I/sad-I-uniprot.txt PANTHER; PTHR43217:SF2; SUCCINATE-SEMIALDEHYDE DEHYDROGENASE [NADP(+)]; 1. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | MODIFY | Summary: The unspecified oxidoreductase reaction is resolved to succinate-semialdehyde oxidation without selecting one nicotinamide cofactor. Reason: PANTHER, the SSADH FunFam and GabD1-like CDD classification agree on succinate-semialdehyde oxidation. They are computational classifications, not independent target enzyme assays. For Sad-I, the NADP-named PTHR43217:SF2 subgroup is a substantive competing cofactor classification against the NAD-dependent FunFam. Neither is dismissed as experimental or privileged merely because it matches GOA. GO:0009013 is a verified descendant of GO:0016491 and specifies the supported substrate while leaving NAD/NADP choice open. Neither the P. putida isoenzymes in PMID:3355840 nor Salmonella YneI in PMID:23229889 establishes a locus-specific 4HB, GABA or putrescine pathway. Proposed replacements: succinate-semialdehyde dehydrogenase [NAD(P)+] activity Supporting Evidence: file:PSEPK/sad-I/sad-I-uniprot.txt FunFam; 3.40.605.10:FF:000012; NAD-dependent succinate-semialdehyde dehydrogenase; 1. file:PSEPK/sad-I/sad-I-uniprot.txt CDD; cd07100; ALDH_SSADH1_GabD1; 1. file:PSEPK/sad-I/sad-I-uniprot.txt PANTHER; PTHR43217:SF2; SUCCINATE-SEMIALDEHYDE DEHYDROGENASE [NADP(+)]; 1. |
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Download this section (compressed HTML)Q: Under which carbon or nitrogen sources is sad-I the physiologically dominant succinate-semialdehyde dehydrogenase?
Q: Does purified PP_2488 accept both NAD and NADP, and are their catalytic efficiencies consistent with the NAD-dependent functional-family assignment?
Experiment: Compare sad-I expression, deletion phenotypes, and NAD- versus NADP-linked succinate-semialdehyde oxidation during growth on 4-hydroxyphenylacetate, putrescine, 4-hydroxybutyrate, and GABA.
Hypothesis: Sad-I contributes to the NAD-preferring SSADH activity induced by 4-hydroxyphenylacetate rather than the NADP-dependent activity induced by putrescine.
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