fol3

Summary: PAINT inference of folylpolyglutamate synthase activity from the shared FolC family. In fungi, dihydrofolate synthetase (Fol3) and folylpolyglutamate synthase (Met7) are separate paralogs; Fol3 adds the first glutamate.

Reason: Family membership only: fol3 belongs to the folylpolyglutamate synthase family (UniProt SIMILARITY; PANTHER PTHR11136; NCBIfam folC), and the PAINT node also covers bifunctional DHFS/FPGS enzymes such as E. coli FolC. No S. pombe assay exists. Within the family fol3 sits in the dihydrofolate synthetase subfamily (PTHR11136:SF0), and its by-similarity curated function is the first glutamate addition, so polyglutamate chain extension is peripheral at best (the met7 paralog carries it); kept as non-core rather than core.

Summary: InterPro family mapping; as above.

Reason: Family membership: the mapping rests on the InterPro folylpolyglutamate synthase signature (IPR001645), which fol3 matches; the same family placement is in UniProt SIMILARITY. No S. pombe assay. The by-similarity curated function is the first glutamate addition (dihydrofolate synthase), so polyglutamate synthase activity is kept as non-core, consistent with the IBA row for this term.

Summary: ATP cosubstrate; subsidiary.

Reason: By similarity to E. coli FolC (P08192): UniProt annotates ATP-binding residues on fol3 transferred from that ortholog, and the curated reaction consumes ATP. ATP binding is part of the ligase mechanism, not a separate function, so it is non-core.

Summary: Phylogenetic inference of location; agrees with the localisation screen.

Summary: ORFeome screen recorded mitochondrial signal; Fol3 is cytosolic in S. cerevisiae.

Reason: Single screen observation.

Summary: PAINT inference of mitochondrion; not specific to the DHFS clade.

Reason: Not established.

Summary: ORFeome YFP screen placed fol3 in the cytosol, consistent with a soluble metabolic enzyme.

Summary: Phylogenetic inference of location; agrees with the localisation screen.

Summary: Mapping from dihydrofolate synthase activity: dihydropteroate + glutamate -> dihydrofolate.

Reason: UniProt's curated function statement (by similarity, ECO:0000250) and catalytic-activity line describe fol3 as the enzyme that adds the first glutamate to 7,8-dihydropteroate, giving 7,8-dihydrofolate; PANTHER places it in the dihydrofolate synthetase subfamily (PTHR11136:SF0) of the folylpolyglutamate synthase family, the clade of S. cerevisiae FOL3. No S. pombe assay is cached (UniProt names it 'Probable'); the claim rests on orthology.

Summary: PAINT inference of dihydrofolate synthase activity (S. cerevisiae FOL3 node).

Reason: UniProt's curated function statement (by similarity, ECO:0000250) and catalytic-activity line describe fol3 as the enzyme that adds the first glutamate to 7,8-dihydropteroate, giving 7,8-dihydrofolate; PANTHER places it in the dihydrofolate synthetase subfamily (PTHR11136:SF0) of the folylpolyglutamate synthase family, the clade of S. cerevisiae FOL3. No S. pombe assay is cached (UniProt names it 'Probable'); the claim rests on orthology.

Summary: EC/RHEA mapping; consistent.

Reason: UniProt's curated function statement (by similarity, ECO:0000250) and catalytic-activity line describe fol3 as the enzyme that adds the first glutamate to 7,8-dihydropteroate, giving 7,8-dihydrofolate; PANTHER places it in the dihydrofolate synthetase subfamily (PTHR11136:SF0) of the folylpolyglutamate synthase family, the clade of S. cerevisiae FOL3. No S. pombe assay is cached (UniProt names it 'Probable'); the claim rests on orthology.

Summary: Correct but broad parent of dihydrofolate biosynthetic process, which this review accepts.

Reason: Action changed from KEEP_AS_NON_CORE: the term is true but general, and its is_a descendant GO:0006761 dihydrofolate biosynthetic process is already carried by the gene (accepted IEA row). The evidence is by similarity (UniProt curated function, ECO:0000250) and family membership: fol3 adds the first glutamate to dihydropteroate, the final step of de novo dihydrofolate synthesis. The PAINT node is not challenged; only the term is refined. Both supported descendants are listed: GO:0006761 dihydrofolate biosynthesis, the step fol3 catalyses, and GO:0046901 tetrahydrofolylpolyglutamate biosynthesis, kept on this gene as the broader pathway its product feeds. GO:0046901 is listed because the rule asks for every supported descendant; it is the pathway the product feeds, retained separately as non-core, not the refinement target for fol3's own step.

Proposed replacements: dihydrofolate biosynthetic process tetrahydrofolylpolyglutamate biosynthetic process

Summary: Correct but broad parent of dihydrofolate biosynthetic process, which this review accepts.

Reason: Action changed from KEEP_AS_NON_CORE, consistent with the IBA row for this term: the term is true but general, and its is_a descendant GO:0006761 dihydrofolate biosynthetic process is already carried by the gene. Evidence is by similarity (UniProt curated function, ECO:0000250): fol3 adds the first glutamate to dihydropteroate to form dihydrofolate. Both supported descendants are listed: GO:0006761 dihydrofolate biosynthesis, the step fol3 catalyses, and GO:0046901 tetrahydrofolylpolyglutamate biosynthesis, kept on this gene as the broader pathway its product feeds. GO:0046901 is listed because the rule asks for every supported descendant; it is the pathway the product feeds, retained separately as non-core, not the refinement target for fol3's own step.

Proposed replacements: dihydrofolate biosynthetic process tetrahydrofolylpolyglutamate biosynthetic process

Summary: Generic InterPro-derived parent of the specific activity, which is already annotated.

Reason: Too general. By similarity (UniProt curated function, ECO:0000250, and catalytic activity EC 6.3.2.12), the acid-amino acid ligation fol3 performs is glutamate addition to dihydropteroate, i.e. dihydrofolate synthase activity, which the gene already carries.

Proposed replacements: dihydrofolate synthase activity

Summary: Curator inference to tetrahydrofolylpolyglutamate synthesis from the polyglutamate synthase IEA; in fungi the polyglutamylation step itself belongs to met7.

Reason: UniProt places fol3 in the tetrahydrofolylpolyglutamate biosynthesis pathway (curated PATHWAY line), and its by-similarity function (ECO:0000250) is the dihydrofolate synthase step that feeds that pathway. No S. pombe experiment. The pathway-level claim is true in this broad sense, but fol3 does not extend the polyglutamate tail, so it is non-core.

Summary: UniPathway mapping; as above.

Reason: The UniPathway mapping corresponds to UniProt's curated PATHWAY line for fol3; by similarity (ECO:0000250) fol3 catalyses the dihydrofolate synthase step of this pathway, not polyglutamate chain extension, so the term is kept as non-core, consistent with the IC row.