Wound-inducible secreted acidic endochitinase of glycoside hydrolase family 19 (class I chitinase). It comprises an N-terminal chitin-binding type-1 (hevein-like) domain joined by a spacer to a C-terminal catalytic chitinase domain, and randomly hydrolyzes the beta-1,4 linkages of chitin and chitodextrins. The enzyme contributes to plant defense against chitin-containing fungal pathogens, and its expression is activated systemically by wounding.
The preferred accession for this review is P16579. These relationships are manually assessed.
REFERENCE PROTEOME CANDIDATE Β· Reviewed 2026-10-19
Reference proteome: UP000006729
Retain P16579 as the primary Swiss-Prot accession. B9HQY4 at POPTR_009G141800v4 is the leading candidate, not an established equivalent. It has 317 identical residues across 340 global-alignment columns (16 substitutions and seven gap columns). B9HQZ1 represents a second model of the same locus, while nearby chitinase loci also match strongly. Hybrid H11-11 provenance and the absence of a direct locus cross-reference leave allele, model, and paralog alternatives unresolved. Mapping source genomic record U01661, including flanks, to the reference assembly is needed before promoting this relationship.
MMseqs2 searched all 77,340 sequences in UP000006729 (release 2026_03); global BLOSUM62 alignments were computed for every returned hit. B9HQY4 ranks first by global alignment score, with 93.2353% identity including gap columns, 97.9412% 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 95.1952% (317/333); gap columns are excluded from this denominator.
file:POPTR/WIN6/WIN6-record-evidence.yaml
query_length: 340 target_length: 333 alignment_columns: 340 identities: 317 mismatches: 16 gap_columns: 7 identity_percent: 93.2353 query_coverage_percent: 97.9412 target_coverage_percent: 100.0
Current UniProtKB and proteome records place B9HQY4, but not P16579, in reference proteome UP000006729. Both UniProt records use NCBITaxon:3694; source-organism qualifications are recorded separately.
file:POPTR/WIN6/WIN6-record-evidence.yaml
reference_proteome: UP000006729 proteome_is_reference: true proteome_taxon_matches: true primary_in_reference_proteome: false alternative_in_reference_proteome: true
UniSave versions 109 (2015), 128 (2020), and 138 (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.
file:POPTR/WIN6/WIN6-record-evidence.yaml
sampled_history_versions: - 109 - 128 - 138 sampled_versions_with_proteome_links: []
ENA assigns the original genomic sequence U01661 to Populus trichocarpa x Populus deltoides, strain H11-11, whereas UniProtKB assigns P16579 to taxon 3694. This hybrid origin is relevant even though the live UniProt taxonomy matches the reference species.
file:POPTR/WIN6/WIN6-record-evidence.yaml
/organism="Populus trichocarpa x Populus deltoides"
file:POPTR/WIN6/WIN6-record-evidence.yaml
/strain="H11-11"
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004568 chitinase activity | IEA GO_REF:0000002 | MODIFY | Summary: General chitinase activity is correct but a more precise endochitinase term is available and better matches the catalytic activity. Reason: The catalytic activity is random endo-hydrolysis of chitin, which is captured precisely by endochitinase activity rather than the broader chitinase parent. Proposed replacements: endochitinase activity Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt Reaction=Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide |
| GO:0005975 carbohydrate metabolic process | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Carbohydrate metabolic process is correct but is a high-level parent term that is less informative than the chitin catabolic process for this specific chitin-degrading enzyme. Reason: The more specific chitin catabolic process and cell wall macromolecule catabolic process terms already capture the biological role; the generic carbohydrate metabolism parent is true but redundant, so it is retained as a non-core annotation. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt Reaction=Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide |
| GO:0006032 chitin catabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: Chitin catabolic process is the direct biological process for this endochitinase. Reason: The enzyme hydrolyzes chitin, so chitin catabolism is the immediate process it participates in. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt Reaction=Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide file:POPTR/WIN6/WIN6-deep-research-openai.md Random endo-hydrolysis of Ξ²-1,4 linkages in chitin/chitodextrins (endochitinase activity). |
| GO:0008061 chitin binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Chitin binding is supported by the N-terminal chitin-binding type-1 domain but is a substrate-binding activity supporting catalysis rather than the core molecular function. Reason: The protein has a dedicated chitin-binding type-1 domain, so chitin binding is well supported, but it is auxiliary to the catalytic endochitinase activity. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt DR GO; GO:0008061; F:chitin binding; IEA:UniProtKB-KW. file:POPTR/WIN6/WIN6-uniprot.txt /note="Chitin-binding type-1" |
| GO:0008843 endochitinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Endochitinase activity is the precise core molecular function, matching the catalytic activity and EC 3.2.1.14. Reason: UniProt records random endo-hydrolysis of chitin under EC 3.2.1.14, which is exactly endochitinase activity. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt Reaction=Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide file:POPTR/WIN6/WIN6-deep-research-openai.md Strongly support `GO:0008843` (endochitinase activity). |
| GO:0016998 cell wall macromolecule catabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: Cell wall macromolecule catabolic process fits degradation of fungal cell wall chitin during defense. Reason: Hydrolysis of chitin, a fungal cell wall polysaccharide, is a cell wall macromolecule catabolic process consistent with the antifungal role. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt FUNCTION: Defense against chitin-containing fungal pathogens. |
| GO:0050832 defense response to fungus | IEA GO_REF:0000117 | ACCEPT | Summary: Defense response to fungus is supported by the documented antifungal function and wound induction. Reason: UniProt states the protein functions in defense against chitin-containing fungal pathogens and is wound-inducible, consistent with an antifungal defense role. Supporting Evidence: file:POPTR/WIN6/WIN6-uniprot.txt FUNCTION: Defense against chitin-containing fungal pathogens. file:POPTR/WIN6/WIN6-deep-research-openai.md Defense against chitin-containing fungal pathogens. |
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Download this section (compressed HTML)Q: Does WIN6 act primarily against fungal pathogens, or does it also contribute to anti-insect defense given its wound-inducible expression?
Experiment: Assay recombinant WIN6 endochitinase activity against chitin substrates and test antifungal inhibition of hyphal growth in vitro.
Type: targeted enzymatic and antifungal assay
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