id: P45730 gene_symbol: PAL product_type: PROTEIN status: DRAFT taxon: id: NCBITaxon:3694 label: Populus trichocarpa description: Cytoplasmic phenylalanine ammonia-lyase (EC 4.3.1.24) catalyzing the first committed, non-oxidative deamination of L-phenylalanine to trans-cinnamate, the entry-point reaction of the phenylpropanoid pathway. Downstream phenylpropanoid metabolism in Populus supplies monolignols/lignin in lignifying xylem and condensed tannins/flavonoids/phenolic glycosides in specialized non-lignifying tissues, with the five-member PtrPAL gene family functionally partitioned between these outputs. alternative_records: - id: A0A2K1XD28 relationship: REFERENCE_PROTEOME_EQUIVALENT reference_proteome: UP000006729 reviewed_on: '2026-10-19' reason: 'Retain P45730 as the primary Swiss-Prot accession. A0A2K1XD28 at POPTR_016G091100 is the manually assessed reference-proteome counterpart: 714/715 identical residues with full ungapped coverage and only R22L. The next full-length family match, A0A2K2A1A8 at POPTR_006G126800, has 32 substitutions and one gap column. The source sequence is from a P. trichocarpa x P. deltoides hybrid; the counterpart assignment is inferred from the sequence comparison and does not establish the parental origin or cause of R22L.' evidence: - type: SEQUENCE_COMPARISON description: MMseqs2 searched all 77,340 sequences in UP000006729 (release 2026_03); global BLOSUM62 alignments were computed for every returned hit. A0A2K1XD28 ranks first by global alignment score, with 99.8601% identity including gap columns, 100.0% query coverage and 100.0% target coverage. The saved candidate table and alignments retain competing matches and residue-level differences. The search is heuristic, and sequence similarity alone is not definitive genomic mapping. Identity over paired residues is 99.8601% (714/715); gap columns are excluded from this denominator. supported_by: - reference_id: file:POPTR/PAL/PAL-record-evidence.yaml supporting_text: |- query_length: 715 target_length: 715 alignment_columns: 715 identities: 714 mismatches: 1 gap_columns: 0 identity_percent: 99.8601 query_coverage_percent: 100.0 target_coverage_percent: 100.0 - type: PROTEOME_MEMBERSHIP description: Current UniProtKB and proteome records place A0A2K1XD28, but not P45730, in reference proteome UP000006729. Both UniProt records use NCBITaxon:3694; source-organism qualifications are recorded separately. supported_by: - reference_id: file:POPTR/PAL/PAL-record-evidence.yaml supporting_text: |- reference_proteome: UP000006729 proteome_is_reference: true proteome_taxon_matches: true primary_in_reference_proteome: false alternative_in_reference_proteome: true - type: RECORD_HISTORY description: UniSave versions 97 (2015), 113 (2020), and 124 (2024) lack Proteomes cross-references. These dated samples support longstanding absence at those dates; they do not establish uninterrupted absence, a removal event, or UniProt's motivation. supported_by: - reference_id: file:POPTR/PAL/PAL-record-evidence.yaml supporting_text: |- sampled_history_versions: - 97 - 113 - 124 sampled_versions_with_proteome_links: [] - type: CURATION_CONTEXT description: Both the Swiss-Prot source citation and ENA L11747 identify a P. trichocarpa x P. deltoides hybrid. The reference proteome is Nisqually. Hybrid provenance makes a small sequence difference plausible but does not itself establish locus identity. supported_by: - reference_id: file:POPTR/PAL/PAL-record-evidence.yaml supporting_text: /organism="Populus trichocarpa x Populus deltoides" existing_annotations: - term: id: GO:0003824 label: catalytic activity evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: Generic catalytic activity is correct but uninformative for a characterized PAL enzyme. action: MODIFY reason: Replace the root catalytic activity term with the specific phenylalanine ammonia-lyase activity term, which captures the actual reaction (L-phenylalanine to trans-cinnamate + NH4+). supported_by: &id_rxn - &id_uniprot_rxn reference_id: file:POPTR/PAL/PAL-uniprot.txt record_section: ["CC:CATALYTIC ACTIVITY"] supporting_text: L-phenylalanine = (E)-cinnamate + NH4(+) - &id_falcon_deamination reference_id: file:POPTR/PAL/PAL-deep-research-falcon.md supporting_text: non-oxidative deamination** of **L-phenylalanine** to yield **trans-cinnamic acid** proposed_replacement_terms: - id: GO:0045548 label: phenylalanine ammonia-lyase activity - term: id: GO:0005737 label: cytoplasm evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: located_in review: summary: Cytoplasm is the reviewed UniProt location for Populus PAL. action: ACCEPT reason: UniProt assigns PAL to the cytoplasm. Falcon notes that the retrieved Populus literature did not independently resolve a subcellular compartment for P45730, so the UniProt cytoplasmic assignment is retained as the best-supported localization. supported_by: - &id_uniprot_cyto reference_id: file:POPTR/PAL/PAL-uniprot.txt record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm' - term: id: GO:0006559 label: L-phenylalanine catabolic process evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: summary: L-phenylalanine catabolic process correctly captures the PAL deamination reaction. action: ACCEPT reason: PAL deaminates L-phenylalanine to trans-cinnamate and ammonium, which is consumption (catabolism) of L-phenylalanine. Supported by the UniProt reaction and the falcon synthesis. supported_by: *id_rxn - term: id: GO:0009611 label: response to wounding evidence_type: IEA original_reference_id: GO_REF:0000117 qualifier: involved_in review: summary: Response to wounding is a plausible downstream/defense context for phenylpropanoid metabolism but is not the core enzymatic function of PAL, and the falcon corpus provides no direct wound-response evidence for Populus PAL. action: KEEP_AS_NON_CORE reason: Retain as non-core. The defense-related role of PAL-derived phenylpropanoids (condensed tannins, phenolic glycosides) is well supported at the pathway level, but a specific wound-response function for this protein is an ARBA electronic inference and is downstream of the committed catalytic step. supported_by: - &id_falcon_defense reference_id: file:POPTR/PAL/PAL-deep-research-falcon.md supporting_text: including **lignin**, **flavonoids**, **condensed tannins (proanthocyanidins)**, and **phenolic glycosides** - term: id: GO:0016841 label: ammonia-lyase activity evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: Ammonia-lyase activity is correct but less specific than phenylalanine ammonia-lyase activity. action: MODIFY reason: Replace the grouping term with the substrate-specific phenylalanine ammonia-lyase activity term, consistent with the UniProt reaction and the falcon entry-reaction description. supported_by: *id_rxn proposed_replacement_terms: - id: GO:0045548 label: phenylalanine ammonia-lyase activity - term: id: GO:0045548 label: phenylalanine ammonia-lyase activity evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables review: summary: Phenylalanine ammonia-lyase activity is the core molecular function of PAL. action: ACCEPT reason: The reaction converts L-phenylalanine to trans-cinnamate and ammonium (EC 4.3.1.24), the committed entry reaction of phenylpropanoid biosynthesis. supported_by: &id_pal_act - *id_uniprot_rxn - &id_falcon_entry reference_id: file:POPTR/PAL/PAL-deep-research-falcon.md supporting_text: the canonical **entry reaction** from aromatic amino-acid metabolism into **phenylpropanoid biosynthesis** - term: id: GO:0046395 label: carboxylic acid catabolic process evidence_type: IEA original_reference_id: GO_REF:0000117 qualifier: involved_in review: summary: Carboxylic acid catabolic process is too broad for the PAL reaction. action: MODIFY reason: The substrate-specific L-phenylalanine catabolic process (already accepted) is the appropriate term; the generic carboxylic acid catabolic grouping adds no information. supported_by: *id_rxn proposed_replacement_terms: - id: GO:0006559 label: L-phenylalanine catabolic process - term: id: GO:0009800 label: cinnamic acid biosynthetic process evidence_type: IEA original_reference_id: GO_REF:0000041 qualifier: involved_in review: summary: Cinnamic acid biosynthetic process is the direct product process of PAL. action: ACCEPT reason: PAL produces trans-cinnamate from L-phenylalanine (UniPathway step 1/1), the committed entry into phenylpropanoid metabolism. Supported by the UniProt pathway statement and the falcon entry-reaction synthesis. supported_by: - &id_uniprot_pathway reference_id: file:POPTR/PAL/PAL-uniprot.txt record_section: ["CC:PATHWAY"] supporting_text: 'trans-cinnamate biosynthesis' - *id_falcon_entry - term: id: GO:0045548 label: phenylalanine ammonia-lyase activity evidence_type: ISS original_reference_id: GO_REF:0000024 qualifier: enables review: summary: Phenylalanine ammonia-lyase activity transferred by sequence similarity from the experimentally characterized ortholog (UniProtKB:P24481). action: ACCEPT reason: The ISS transfer is well founded; PAL is a conserved member of the PAL/histidase family with the autocatalytic MIO active site, and the reaction is the same committed deamination of L-phenylalanine to trans-cinnamate. references: - id: file:POPTR/PAL/PAL-record-evidence.yaml title: Compact archived record and sequence evidence for P45730 - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: - statement: GO_REF:0000002 supplied one or more source GOA annotations reviewed in this file. - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: - statement: GO_REF:0000120 supplied one or more source GOA annotations reviewed in this file. - id: GO_REF:0000117 title: Electronic Gene Ontology annotations created by ARBA machine learning models findings: - statement: GO_REF:0000117 supplied one or more source GOA annotations reviewed in this file. - id: GO_REF:0000041 title: Gene Ontology annotation based on UniPathway vocabulary mapping findings: - statement: GO_REF:0000041 supplied one or more source GOA annotations reviewed in this file. - id: GO_REF:0000024 title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity findings: - statement: GO_REF:0000024 supplied one or more source GOA annotations reviewed in this file. - id: file:POPTR/PAL/PAL-uniprot.txt title: UniProtKB reviewed entry for PAL (PALY_POPTR, P45730) findings: - record_section: ["CC:CATALYTIC ACTIVITY"] supporting_text: L-phenylalanine = (E)-cinnamate + NH4(+) reference_section_type: DATABASE_ENTRY - record_section: ["CC:PATHWAY"] supporting_text: 'PATHWAY: Phenylpropanoid metabolism' reference_section_type: DATABASE_ENTRY - record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm' reference_section_type: DATABASE_ENTRY - record_section: ["CC:SIMILARITY"] supporting_text: 'SIMILARITY: Belongs to the PAL/histidase family' reference_section_type: DATABASE_ENTRY - id: file:POPTR/PAL/PAL-goa.tsv title: QuickGO GOA annotations for PAL findings: - statement: GOA rows supplied the existing_annotations reviewed in this file. - id: file:POPTR/PAL/PAL-deep-research-falcon.md title: Falcon (Edison) deep-research synthesis for Populus trichocarpa PAL (P45730) findings: - supporting_text: catalyzes the **non-oxidative deamination** of **L-phenylalanine** to yield **trans-cinnamic acid**, which constitutes the canonical **entry reaction** from aromatic amino-acid metabolism into **phenylpropanoid biosynthesis** in plants reference_section_type: OTHER - supporting_text: PAL is consistently described as controlling or strongly influencing **carbon flux** into phenylpropanoid-derived products, including **lignin**, **flavonoids**, **condensed tannins (proanthocyanidins)**, and **phenolic glycosides** reference_section_type: OTHER - supporting_text: '**Populus trichocarpa contains five PAL genes (PtrPAL1–PtrPAL5)**' reference_section_type: OTHER - supporting_text: a **lignin-associated, xylem/root-tip-enriched group** versus a more broadly expressed group more associated with **condensed tannins/flavonoids/other phenolics** reference_section_type: OTHER - supporting_text: The retrieved Populus-focused excerpts do not provide a definitive subcellular compartment assignment (e.g., cytosol vs ER/microsomes) for **Populus trichocarpa** PAL proteins reference_section_type: OTHER - supporting_text: Phenylalanine ammonia-lyase (EC 4.3.1.24) catalyzing deamination of **L-phenylalanine → trans-cinnamic acid**, the entry reaction into phenylpropanoid metabolism reference_section_type: OTHER core_functions: - description: Catalyzes the non-oxidative deamination of L-phenylalanine to trans-cinnamate (EC 4.3.1.24), the committed entry reaction of phenylpropanoid biosynthesis, supplying carbon flux to downstream lignin, flavonoid, and condensed-tannin metabolism. molecular_function: id: GO:0045548 label: phenylalanine ammonia-lyase activity directly_involved_in: - id: GO:0006559 label: L-phenylalanine catabolic process - id: GO:0009800 label: cinnamic acid biosynthetic process locations: - id: GO:0005737 label: cytoplasm supported_by: - *id_uniprot_rxn - *id_uniprot_cyto - *id_falcon_entry proposed_new_terms: [] suggested_questions: - question: Which Populus tissues and stresses induce this PAL isoform relative to the other four PtrPAL paralogs (PtrPAL1-PtrPAL5)? - question: Does this PAL isoform preferentially support lignin (xylem/monolignol flux) versus condensed-tannin/flavonoid phenylpropanoid output? suggested_experiments: - description: Measure phenylalanine-to-cinnamate conversion and downstream phenylpropanoid metabolite pools (monolignols, flavonoids, condensed tannins) after PAL knockdown or overexpression in Populus. experiment_type: targeted functional assay - description: Map this PAL isoform to a specific Potri locus and resolve its subcellular localization (cytosol vs microsomal/ER association) by fractionation and fluorescent-protein fusion, since the retrieved literature did not resolve the compartment for P45730. experiment_type: localization and isoform-mapping study