cbl1 (SPCC11E10.01) encodes the fission yeast cystathionine beta-lyase (EC 4.4.1.13), a pyridoxal 5'-phosphate-dependent enzyme of the trans-sulfuration family (PTHR11808:SF50, the same subfamily as S. cerevisiae STR3). It cleaves L-cystathionine to L-homocysteine, pyruvate and ammonium, the second step of forward trans-sulfuration that follows cystathionine gamma-synthase (met3) and supplies homocysteine for de novo methionine synthesis; like other members it can also cleave other S-substituted cysteines (cysteine-S-conjugate beta-lyase activity). Its role is inferred from orthology; it is predicted to be cytoplasmic, and unlike S. cerevisiae Str3 it lacks a C-terminal PTS1-like peroxisomal targeting signal.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from node PTN000211590 (donors include S. cerevisiae STR3/CYS3, Arabidopsis CBL/CGS1, mouse Cth). Cytoplasm is consistent with UniProt's prediction for S. pombe Cbl1, which, unlike Str3, has no C-terminal PTS1. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0086 Cytoplasm, by similarity to S. cerevisiae Cys3); acceptable. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0005777 peroxisome | ISS GO_REF:0000024 | UNDECIDED | Summary: PomBase ISS from S. cerevisiae Str3 (P53101), which is peroxisomal via a C-terminal PTS1. The S. pombe protein ends in ...ANFKQN, which is not a canonical PTS1, and no S. pombe localisation data are available in our sources; the curator may have had additional information (e.g. a PTS2 or proteomics). Reason: Cannot verify the peroxisomal transfer; sequence features do not support it, but it is a curator ISS call, so neither accepted nor removed. Not used for core location. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0006790 sulfur compound metabolic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO (IPR006238, cystathionine beta-lyase, eukaryotic) to 'sulfur compound metabolic process'; correct but very general. Reason: Broad parent of the core process. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt pathway; L-homocysteine from L-cystathionine: step 1/1. |
| GO:0016846 carbon-sulfur lyase activity | IBA GO_REF:0000033 | TOO GENERAL | Summary: PAINT IBA (PTN000211590) to 'carbon-sulfur lyase activity'; a correct parent of cysteine-S-conjugate beta-lyase activity. The PAINT node sits at this level because it spans gamma-lyases and beta-lyases. Reason: Correct but generic; the specific activity GO:0047804 is annotated separately. Same call as for STR3. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=L,L-cystathionine + H2O = L-homocysteine + pyruvate + NH4(+); |
| GO:0019346 obsolete transsulfuration | IBA GO_REF:0000033 | MODIFY | Summary: PAINT IBA (PTN000211590) to obsolete 'transsulfuration'. GO:0019346 'transsulfuration' is obsolete (it conflated forward and reverse directions); cystathionine beta-lyase acts in the forward, homocysteine-forming direction. Reason: Obsolete term; replace with L-homocysteine biosynthesis, as in the S. cerevisiae STR3 review. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000211590 · PTN000211590 SUPPORTS TRANSFER Node placement is sound; the propagated term is now obsolete. Proposed replacements: L-homocysteine biosynthetic process Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=L,L-cystathionine + H2O = L-homocysteine + pyruvate + NH4(+); file:SCHPO/cbl1/cbl1-uniprot.txt pathway; L-homocysteine from L-cystathionine: step 1/1. |
| GO:0019346 obsolete transsulfuration | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO (IPR000277) to obsolete 'transsulfuration'. GO:0019346 'transsulfuration' is obsolete (it conflated forward and reverse directions); cystathionine beta-lyase acts in the forward, homocysteine-forming direction. Reason: Obsolete term; replace with GO:0071269. Proposed replacements: L-homocysteine biosynthetic process Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=L,L-cystathionine + H2O = L-homocysteine + pyruvate + NH4(+); |
| GO:0030170 pyridoxal phosphate binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBA (PTN000211590) to pyridoxal phosphate binding; correct cofactor property of this PLP enzyme. Reason: Correct cofactor annotation, non-core. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Name=pyridoxal 5'-phosphate; Xref=ChEBI:CHEBI:597326; |
| GO:0030170 pyridoxal phosphate binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro2GO (IPR000277) to pyridoxal phosphate binding; correct cofactor property. Reason: Correct cofactor annotation, non-core. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Name=pyridoxal 5'-phosphate; Xref=ChEBI:CHEBI:597326; |
| GO:0047804 cysteine-S-conjugate beta-lyase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA (ARBA, IPR006238, RHEA:13965/18121, EC 4.4.1.13) to cysteine-S-conjugate beta-lyase activity, which now subsumes the obsolete cystathionine beta-lyase term; core activity. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=L,L-cystathionine + H2O = L-homocysteine + pyruvate + NH4(+); file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=an S-substituted L-cysteine + H2O = a thiol + pyruvate + |
| GO:0047804 cysteine-S-conjugate beta-lyase activity | ISS GO_REF:0000024 | ACCEPT | Summary: PomBase ISS from S. cerevisiae STR3 (biochemically characterised cystathionine beta-lyase in the same PANTHER subfamily); core activity. Supporting Evidence: file:SCHPO/cbl1/cbl1-uniprot.txt Reaction=L,L-cystathionine + H2O = L-homocysteine + pyruvate + NH4(+); |
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