| Claim | Details (quote-like paraphrase) | Source (with year, journal) | URL | Evidence context ID |
|---|---|---|---|---|
| *S. pombe* appears to have only one GH18 chitinase gene | “Comparative genome analysis places *Schizosaccharomyces pombe* at the extreme low end of fungal GH18 copy number, with 1 GH18 gene total.” | Karlsson & Stenlid 2008, *Evolutionary Bioinformatics* | https://doi.org/10.4137/ebo.s604 | (pqac-00000004, pqac-00000005) |
| Reviews also state that *S. pombe* encodes a single GH18 chitinase | “The number of fungal chitinases varies widely, from only one GH18 family member in the yeast *Schizosaccharomyces pombe* to >30 in some filamentous fungi.” | Langner & Göhre 2016, *Current Genetics* | https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000006, pqac-00000007) |
| Vegetative *S. pombe* cell walls are generally described as lacking chitin | “The vegetative cell wall of fission yeast lacks chitin, although chitin has been detected in the conidial/spore wall.” | Teparić et al. 2020, *International Journal of Molecular Sciences* | https://doi.org/10.3390/ijms21238996 | (pqac-00000000) |
| Therefore any *S. pombe* chitinase likely acts on restricted or stage-specific chitin-containing structures | “Because vegetative walls are described as chitin-poor/without chitin, a GH18 enzyme in *S. pombe* is unlikely to be a bulk wall-remodeling enzyme for general vegetative wall turnover.” | Inference from Teparić et al. 2020 plus fungal chitinase reviews | https://doi.org/10.3390/ijms21238996 | (pqac-00000000, pqac-00000006) |
| Cell separation in *S. pombe* is known to rely primarily on glucanases, especially Eng1 | “In fission yeast, failure of cell separation is mainly linked to inability to degrade the β-1,3-glucan-rich primary septum; Eng1 is required for primary septum dissolution.” | Adams 2004, *Microbiology*; Roncero & Vázquez de Aldana 2019, book chapter | https://doi.org/10.1099/mic.0.26980-0 ; https://doi.org/10.1007/82_2019_185 | (pqac-00000001, pqac-00000003) |
| This argues against assigning cts2/Q9C105 as the principal septum-dissolving enzyme in *S. pombe* without direct evidence | “Unlike budding yeast Cts1, the best-established fission-yeast cell-separation hydrolase is a glucanase, so a direct cytokinetic role for Q9C105 remains plausible but unproven.” | Synthesis from Adams 2004 and Roncero & Vázquez de Aldana 2019 | https://doi.org/10.1099/mic.0.26980-0 ; https://doi.org/10.1007/82_2019_185 | (pqac-00000001, pqac-00000003) |
| GH18 chitinases hydrolyze β-1,4-linked GlcNAc polymers | “Chitinases (EC 3.2.1.14) hydrolyze bonds between N-acetylglucosamine residues in chitin/chito-oligosaccharides.” | Karlsson & Stenlid 2008, *Evolutionary Bioinformatics*; Langner & Göhre 2016, *Current Genetics* | https://doi.org/10.4137/ebo.s604 ; https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000004, pqac-00000006) |
| GH18 enzymes can be endo-acting or exo-acting | “Family 18 chitinases share a common catalytic mechanism but may cleave internally in the polymer or processively from one end depending on active-site architecture.” | Langner & Göhre 2016, *Current Genetics* | https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000006, pqac-00000007) |
| Canonical GH18 catalytic chemistry supports predicted hydrolase activity for Q9C105 | “GH18 chitinases use a neighboring-group participation mechanism; a conserved catalytic glutamate within a DxxDxDxE-type motif functions as general acid/base.” | Langner & Göhre 2016, *Current Genetics* | https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000007) |
| Cell-wall-associated chitinases in fungi commonly function in remodeling during growth/division | “Across fungi, chitinases are implicated in cell wall plasticity, cell division, septum remodeling, morphogenesis, autolysis, and developmental transitions.” | Adams 2004, *Microbiology*; Langner & Göhre 2016, *Current Genetics* | https://doi.org/10.1099/mic.0.26980-0 ; https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000002, pqac-00000006) |
| Likely localization for a precursor GH18 chitinase is the secretory pathway/extracellular cell surface | “Given the UniProt designation as a precursor and the known extracellular/cell-wall roles of fungal chitinases, the most likely working location is secreted/periplasmic/cell-wall associated rather than cytosolic.” | Inference from fungal chitinase biology in reviews | https://doi.org/10.1099/mic.0.26980-0 ; https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000002, pqac-00000006) |
| Identity caveat: direct literature linking cts2 to Q9C105/SPAPB1E7.04c was not retrieved | “Available retrieved papers support the existence of a single *S. pombe* GH18 chitinase, but no primary paper in the current evidence set explicitly maps gene symbol cts2 to UniProt Q9C105/SPAPB1E7.04c.” | Current evidence synthesis from retrieved literature set | https://doi.org/10.4137/ebo.s604 ; https://doi.org/10.1007/s00294-015-0530-x | (pqac-00000004, pqac-00000006) |


*Table: This table summarizes the strongest evidence extracted so far that is relevant to annotating the fission-yeast protein Q9C105/cts2. It distinguishes direct organism-level facts from cautious functional inferences, which is especially important because explicit literature mapping of cts2 to Q9C105 was not retrieved.*