PvdD (PP_4219) is a large cytosolic nonribosomal peptide synthetase required for pyoverdine biosynthesis in Pseudomonas putida KT2440. Its repeated adenylation, condensation and phosphopantetheine carrier domains assemble the peptide scaffold, and its terminal thioesterase supports product release. Loss of pvdD abolishes pyoverdine production and impairs siderophore-dependent iron acquisition. The precise monomer specificity of its three modules has not been established in the inspected target-specific evidence.
Definition: A multienzyme complex composed of pyoverdine biosynthetic enzymes that assemble and offload the pyoverdine peptide scaffold during pyoverdine biosynthesis.
Justification: Automated annotations currently over-transfer the enterobactin-specific complex term to pyoverdine NRPS proteins because GO lacks a pyoverdine-specific synthetase complex term.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | ACCEPT | Summary: Retain catalytic activity of the pyoverdine NRPS. Reason: PvdD directly catalyzes amino-acid activation and peptide assembly. A broad catalytic ancestor remains valid even when a specific NRPS term is available. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md NRPSs are large modular enzymes that assemble peptides via a thiotemplate mechanism file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | ACCEPT | Summary: Retain cytoplasmic localization. Reason: Pyoverdine precursor assembly occurs in the cytoplasm. Cytoplasm and cytosol are compatible; their overlap does not refute either localization. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md NRPSs are large modular enzymes that assemble peptides via a thiotemplate mechanism file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase |
| GO:0005829 cytosol | IEA GO_REF:0000118 | ACCEPT | Summary: Appropriate localization for a giant soluble NRPS that lacks membrane-targeting features and operates prior to pyoverdine export and periplasmic maturation. Reason: Cytosol is the correct localization. Falcon deep research confirms PvdD-mediated peptide assembly occurs in the cytoplasm before precursor export across the inner membrane and periplasmic maturation. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md pyoverdine synthesis begins in the cytoplasm file:PSEPK/pvdD/pvdD-deep-research-falcon.md PvdI/PvdJ/PvdD explore the cytoplasm |
| GO:0009239 enterobactin biosynthetic process | IEA GO_REF:0000118 | MODIFY | Summary: Incorrect specific process. P. putida KT2440 produces pyoverdine rather than enterobactin, so the correct process term is pyoverdine biosynthetic process. Reason: The enterobactin process is an over-transfer error. Falcon deep research confirms PvdD is the pyoverdine NRPS in KT2440 and that a pvdD mutant does not produce pyoverdine, so the correct process is pyoverdine biosynthesis, not enterobactin. Proposed replacements: pyoverdine biosynthetic process Supporting Evidence: file:PSEPK/pvdD/pvdD-notes.md Enterobactin-specific terms in the seeded GOA are incorrect for `pvdD`; they should be replaced with pyoverdine- or siderophore-specific process terms. file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase |
| GO:0009366 enterobactin synthetase complex | IEA GO_REF:0000118 | REMOVE | Summary: Incorrect complex term. PvdD belongs to the pyoverdine NRPS assembly line, not the enterobactin synthetase complex, and GO currently lacks a pyoverdine-specific synthetase complex term. Reason: The target PP_4219 genetic evidence and modular NRPS architecture establish a pyoverdine biosynthetic enzyme, not an enterobactin synthetase subunit. The shared nonribosomal assembly chemistry is insufficient for this specific complex assignment. The exact P. aeruginosa PvdL/PvdI/PvdJ/PvdD assembly composition is comparative, not established for this target. Supporting Evidence: file:PSEPK/pvdD/pvdD-notes.md GO has `pyoverdine biosynthetic process` but lacks a pyoverdine-specific synthetase complex term; this absence likely drives over-transfer to `enterobactin synthetase complex`. file:PSEPK/pvdD/pvdD-deep-research-falcon.md PvdI/PvdJ/PvdD explore the cytoplasm |
| GO:0031177 phosphopantetheine binding | IEA GO_REF:0000120 | ACCEPT | Summary: Retain phosphopantetheine binding by the carrier modules. Reason: Q88F79 contains three phosphopantetheine-bearing carrier domains. This specific cofactor-binding term is supported and need not be discarded because carrier activity describes the integrated role more fully. The carrier-activity term remains in the core synthesis. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md covalently tethers the activated monomer on a phosphopantetheine arm |
| GO:0043041 amino acid activation for nonribosomal peptide biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: Amino-acid activation is a core step performed by PvdD. Reason: Its adenylation domains directly activate monomers for the nonribosomal assembly reaction. A mechanistic subprocess of the defining activity is core, not incidental. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md NRPSs are large modular enzymes that assemble peptides via a thiotemplate mechanism file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase |
| GO:0044550 secondary metabolite biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: Retain secondary-metabolite biosynthesis. Reason: Pyoverdine is a secondary metabolite and PvdD directly builds its peptide scaffold. The broad process is valid; a siderophore-specific term does not contradict it. Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md NRPSs are large modular enzymes that assemble peptides via a thiotemplate mechanism file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase |
| GO:0047527 2,3-dihydroxybenzoate-serine ligase activity | IEA GO_REF:0000118 | MODIFY | Summary: Wrong substrate/product and wrong siderophore family. PvdD is not the enterobactin enzyme EntF; the analogous correct activity is amino acid ligation by a non-ribosomal peptide synthase. Reason: The target is a pyoverdine NRPS with target PP_4219 genetic and domain support; DHB-serine ligation is the distinct enterobactin chemistry. Keep the NRPS amino-acid-ligation replacement without assigning the threonine-rich substrate map of P. aeruginosa PvdD to this three-module KT2440 protein. Proposed replacements: amino acid ligation activity by nonribosomal peptide synthase Supporting Evidence: file:PSEPK/pvdD/pvdD-deep-research-falcon.md pvdD is explicitly identified as PP_4219 encoding a pyoverdine nonribosomal peptide synthetase file:PSEPK/pvdD/pvdD-deep-research-falcon.md Direct KT2440 biochemical substrate-assignment for Q88F79 was not found |
| GO:0072330 monocarboxylic acid biosynthetic process | IEA GO_REF:0000117 | REMOVE | Summary: KT2440 pyoverdines are polycarboxylic, so their synthesis does not support a monocarboxylic-acid biosynthesis row. Reason: The focused structural accounting found that native KT2440 pyoverdine variants carry two or three free carboxylic acid groups. GO:0072330 is therefore chemically inapt, because it describes formation of acids with one carboxyl group. PvdD's direct role is nonribosomal assembly of the pyoverdine peptide scaffold; the ARBA monocarboxylic-acid call is a broad automated over-annotation. Supporting Evidence: PMID:25895945 The three PVDs of P. putida possess the same peptide chain of seven amino acids, Asp-Orn-OHAsp-Dab-Gly-Ser-cOHOrn, with a cyclicized portion present in two of the PVDs. file:PSEPK/pvdD/pvdD-hypotheses/pyoverdine-structure-and-monocarboxylate-biosynthesis/openscientist.md The hypothesis's chemical-class reasoning, applied rigorously, lands on refutation. |
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Download this section (compressed HTML)Q: Which amino acid substrate is selected by each adenylation module of KT2440 PvdD, and how does that map onto the G4R/G4R A pyoverdine peptide products?
Q: Does PvdD form a stable biosynthetic complex with PvdI, PvdJ, and PvdL, or are the pyoverdine NRPS proteins coordinated through transient module handoffs?
Q: Which phosphopantetheinyl transferase activates the three carrier domains of PvdD in KT2440, and is that activation regulated by iron availability?
Experiment: Clone and purify individual adenylation modules or module pairs from PvdD and test substrate preference by ATP-PPi exchange or adenylation assays with candidate amino acids from the KT2440 pyoverdine peptide.
Hypothesis: PvdD adenylation modules have distinct substrate specificities that determine the KT2440 pyoverdine peptide sequence.
Type: biochemical assay
Experiment: Mutate the conserved phosphopantetheinylated serine in each carrier domain and measure pyoverdine production and intermediate accumulation by LC-MS.
Hypothesis: The carrier domains of PvdD are required as active phosphopantetheine-tethered intermediates during pyoverdine assembly.
Type: mutagenesis study
Experiment: Test interaction of PvdD with PvdI, PvdJ, and PvdL by co-immunoprecipitation, cross-linking mass spectrometry, or bacterial two-hybrid assays under iron-limited conditions.
Hypothesis: PvdD participates in a coordinated pyoverdine NRPS assembly line in the cytosol.
Type: protein interaction study
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