GALNT3

Summary: GALNT3 has an established Golgi membrane location, including in the curated disease-event context.

Reason: The cited FailedReaction R-HSA-5096537 uses a Q14435 variant set at the Golgi membrane and links the normal reaction. Preserve this disease context; do not interpret failure of catalysis as proof of normal mutant activity. Independent normal-target records and human localization evidence support the gene-level Golgi membrane location.

Summary: The normal FGF23 glycosylation reaction places GALNT3 at the Golgi membrane.

Reason: R-HSA-8851619 resolves its catalyst to human GALNT3/Q14435 at GO:0000139. The model distinguishes the membrane-associated enzyme from lumenal FGF23 and nucleotide-sugar reactants. Human Golgi localization and the type-II membrane architecture support this functional location.

Summary: The normal mucin glycosylation catalyst set includes Golgi membrane GALNT3.

Reason: The R-HSA-913675 catalyst set explicitly includes human GALNT3/Q14435 at the Golgi membrane. This is consistent with independent human localization and membrane-anchored architecture. The curated set is not evidence that every GALNT has identical acceptor specificity.

Summary: GALNT3 inherits experimentally grounded polypeptide GalNAc-transferase activity (GO_REF:0000033; PMID:9295285).

Reason: The actual PAINT assertion at PTN004287905 lies on the human GALNT3 lineage, and the aligned target sequence matches the canonical human protein. No target-path loss was found. Human recombinant GALNT3 transfers GalNAc from UDP-GalNAc to peptide acceptors, independently supporting the inherited catalytic function. The target among the descendant evidences is legitimate experimental grounding, not circularity.

Summary: GALNT3 catalyses FGF23 O-GalNAc addition at its protease-sensitive region (PMID:16638743).

Reason: The authentic abstract and selected indexed original Methods/Results support human GALNT3-dependent FGF23 glycosylation and peptide assays. Later human biochemical and cell experiments confirm the catalytic and lectin-dependent mechanism. Preserve the literal FGF23 input. This supports transferase activity; the older title does not establish that GALNT3 universally increases the rate of FGF23 secretion.

Summary: Human GALNT3 glycosylates FGF23 Thr178 through catalytic and lectin-domain cooperation (PMID:31932717).

Reason: Human soluble enzyme assays and human GALNT3 expression in CHO cells support GalNAc transfer to FGF23, with prior Thr171 glycosylation and a functioning lectin domain facilitating Thr178 modification. The crystal complexes in this paper are zebra finch GALNT3, whereas the human biochemical, cell, AFM and SAXS experiments provide the target evidence. Preserve the FGF23 input and do not equate the engineered soluble constructs with the natural short product.

Summary: An engineered soluble human GALNT3 transfers GalNAc to peptide acceptors (PMID:8663203).

Reason: The original selected Methods/Results and Table I describe human GALNT3 expressed without its membrane anchor in Sf9 cells. Culture-supernatant assays measure radiolabeled UDP-GalNAc incorporation into Muc2, Muc5c and an HIV-V3 peptide against control supernatants. This establishes the catalytic activity; the synthetic viral peptide is not evidence for a physiological role in HIV infection, and the engineered deletion is not the natural 192-residue product.

Summary: Purified human GALNT3 has UDP-GalNAc-dependent peptide glycosyltransferase activity (PMID:9295285).

Reason: Purified soluble human GALNT3 made in insect cells glycosylates peptide substrates, with donor specificity and site-dependent kinetic measurements. This directly establishes the molecular function. The activity of the engineered catalytic preparation is not automatically assigned to the natural short splice product.

Summary: The combined electronic annotation agrees with measured human GalNAc-transferase activity (PMID:9295285).

Reason: Human recombinant GALNT3 has the stated donor-dependent peptide glycosylation activity. GO_REF:0000120 combines overlapping automated provenance; the ARBA, orthology and EC inputs are not counted as independent experiments. The functional claim is accepted on the human biochemical evidence, without asserting that every current rule condition was separately audited.

Summary: GALNT3 and FGF23 site variants support a substrate-specific glycosylation interaction (PMID:17129170).

Reason: The retained original study combines GALNT3 silencing with FGF23 expression and examines glycosylation/processing, including the Thr178 region. Preserve FGF23 as the literal genetic-interaction source. These cellular results agree with independently measured GALNT3 catalytic activity; they do not imply that FGF23 itself is a glycosyltransferase or that this row is an additional purified-enzyme measurement.

Summary: GALNT3 perturbation changes FGF23 glycosylation and processing in human cells (PMID:17129170).

Reason: The original selected Methods/Results use human HOS-TE85 cells, GALNT3 siRNAs and an FGF23 expression construct; reduced GALNT3 shifts intact FGF23 toward processed fragments. This is perturbation evidence in a cellular substrate-processing system, not a purified-enzyme assay. Independent human recombinant assays establish that the causal molecular activity is polypeptide GalNAc transfer.

Summary: The GALNT3 gene encodes the experimentally established GalNAc-transferase activity (PMID:9592121; PMID:9295285).

Reason: PMID:9592121 is an authentic human gene-organization/chromosome study whose accessible abstract identifies the transferase family; its full experimental text was not recovered. The catalytic claim is nevertheless directly established by the independent human expression and purified-enzyme studies. Retain the true activity without presenting genomic mapping as a new enzymatic assay.

Summary: Normal human GALNT3 catalyses GalNAc transfer, while the cited Reactome event models its failure in variants.

Reason: R-HSA-5096537 explicitly describes a FailedReaction with GALNT3 variants C574G, Q592*, R162* and T272K and links normalReaction R-HSA-913675. It is not positive evidence that those mutant proteins retain normal catalysis. The gene-level wild-type function is established independently by normal GALNT3 catalyst records and human biochemical experiments; retain that function while preserving the disease-event provenance.

Summary: Reactome explicitly models human GALNT3 catalysis of FGF23 GalNAc addition.

Reason: The original ContentService chain for R-HSA-8851619 resolves its catalyst through physical entity R-HSA-913620 to human Q14435. It models UDP-GalNAc-dependent FGF23 modification with the enzyme at the Golgi membrane and substrate in the Golgi lumen. This is a curated reaction representation corroborated by human biochemical/cell evidence, not a new experiment.

Summary: GALNT3 is an explicit member of the normal Reactome mucin GalNAc-transferase catalyst set.

Reason: R-HSA-913675 uses catalyst R-HSA-913697 and set R-HSA-913644, whose hasMember chain includes human GALNT3/Q14435. Human peptide assays independently demonstrate mucin-sequence acceptor glycosylation. Set membership supports the catalytic class without asserting identical site preferences for every GALNT family member.

Summary: The calcium-substitution activity result does not resolve direct calcium binding (PMID:9295285).

Reason: Purified human GALNT3 showed no detectable Muc2 glycosylation when calcium replaced manganese at 5, 10 or 20 mM. This is negative evidence for calcium-supported turnover, not a direct measurement of calcium binding. The manganese-only UniProt features, ricin B-type lectin fold and absence of a comparable GALNT1 calcium annotation do not establish that GALNT3 cannot bind calcium. No positive calcium-cofactor function is inferred. Retain UNDECIDED for the specific ion-binding assertion because the available observations do not distinguish binding without catalysis from absence of binding.

Summary: The broad cytoplasmic location can be refined to the established Golgi apparatus.

Reason: Cytoplasm includes organelles and is not synonymous with cytosol. The literal mouse P70419 donor has current experimental cytoplasm support, although its underlying localization study was not independently read here. Human GALNT3 localization to the Golgi is established independently, and GO:0005794 is part_of GO:0005737. Refine to that organelle without claiming the original compartment assertion is false.

Proposed replacements: Golgi apparatus

Summary: GALNT3 inherits a supported Golgi apparatus location (GO_REF:0000033).

Reason: The actual PTN000187024 Golgi assertion lies on the human GALNT3 lineage, with no target-path negative placement. Human localization experiments independently support Golgi residence. The organelle term is informative and retained; more detailed membrane annotations do not make this valid organelle annotation an error.

Summary: The Human Protein Atlas supports GALNT3 localization to the Golgi apparatus.

Reason: The current HPA subcellular record lists Golgi apparatus with supported reliability under its immunofluorescence curation method. Individual images were not independently rescored. Human HeLa localization experiments provide corroborating target evidence, and the organelle-level claim is retained.

Summary: Human GALNT3 is localized to the Golgi apparatus (PMID:9394011).

Reason: Golgi localization is directly supported by the human HeLa fractionation, immunofluorescence and immunoelectron-microscopy results summarized in PMID:9394011, and by the current Human Protein Atlas location record. PMID:12506059 establishes ocular epithelial GALNT3 expression, but its full target-specific localization panels were not recovered. Retain the independently established organelle location without claiming those ocular panels were read.

Summary: The inherited O-glycosylation process is specifically O-GalNAc glycosylation (GO_REF:0000033).

Reason: The actual PTN004287905 assertion is on the GALNT3 lineage, with no target-path loss; the inherited broad process is biologically sound. Human donor/substrate assays identify its O-GalNAc mechanism. Refine to GO:0016266, which has a direct is_a relationship to GO:0006493. This is term precision, not a claim of defective ancestral placement or circular target evidence.

Proposed replacements: protein O-linked glycosylation via N-acetylgalactosamine

Summary: Human GALNT3 initiates O-linked glycosylation specifically through GalNAc transfer (PMID:8663203).

Reason: The human soluble-enzyme expression study measures incorporation from UDP-GalNAc into peptide acceptors. This directly supports the O-GalNAc-specific descendant GO:0016266. Refine the broad parent process without disputing the observed activity or turning an engineered expression construct into a natural product.

Proposed replacements: protein O-linked glycosylation via N-acetylgalactosamine

Summary: The orthology-supported process can be specified as protein O-GalNAc glycosylation.

Reason: The literal mouse Galnt3 donor P70419 is correctly identified and its current GOA contains experimental O-glycosylation support. The underlying donor papers were not independently read here. Direct human biochemical evidence establishes the narrower process GO:0016266, an is_a child of the asserted broad O-linked glycosylation term; refinement does not reject the orthology or donor biology.

Proposed replacements: protein O-linked glycosylation via N-acetylgalactosamine

Summary: GALNT3-dependent FGF23 processing reflects O-GalNAc glycosylation (PMID:17129170).

Reason: The human-cell silencing and substrate-processing experiments support GALNT3 involvement in glycosylation, and direct human enzyme studies establish the transferred sugar as GalNAc. Replace the correct broad process with its supported is_a child GO:0016266. The clinical phosphate phenotype remains a consequence of altered FGF23 handling, not an additional catalytic activity.

Proposed replacements: protein O-linked glycosylation via N-acetylgalactosamine

Summary: GALNT3 glycosylates FGF23 upstream of receptor-triggered signaling.

Reason: R-HSA-190372 genuinely includes the GALNT3-catalysed FGF23 glycosylation event R-HSA-8851619. That upstream chemical step affects intact FGF23 availability and has clear regulatory relevance. GO:0008543, however, defines the molecular signals generated as a consequence of FGFR binding its ligand; pathway membership does not establish GALNT3 execution of those receptor-triggered signals. Mark this process assignment as over-annotated while preserving the valid target/source membership and glycosylation role.

Summary: The membrane-associated enzyme is more specifically localized to the Golgi membrane.

Reason: PMID:8663203 identifies a type-II membrane architecture and tests an engineered soluble form; independent human localization establishes the Golgi compartment. Refine the broad membrane term to GO:0000139 along the verified is_a path through organelle membrane. This does not infer physiological soluble localization from the experimental anchor deletion.

Proposed replacements: Golgi membrane

Summary: GALNT3 performs FGF23 O-GalNAc glycosylation (PMID:16638743).

Reason: The authentic abstract and selected indexed original human transfection/peptide evidence support addition of GalNAc at the FGF23 protease-sensitive region. The later human enzyme and cell work confirms the mechanism. This is direct chemical participation, not merely a requirement inferred from disease. Intact hormone accumulation must be distinguished from an increase in secretion rate.

Summary: Human GALNT3 directly performs lectin-assisted FGF23 O-GalNAc glycosylation (PMID:31932717).

Reason: Human enzyme assays and cell experiments establish GalNAc addition, with prior Thr171 glycosylation facilitating Thr178 modification. Both catalytic and lectin-domain function are required in the tested system. The short pulse-labeling experiment did not show markedly increased secretion; the later excess of intact extracellular hormone was attributed mainly to stability after secretion. The O-GalNAc process itself is directly supported.

Summary: Purified human GALNT3 adds GalNAc to peptide acceptors (PMID:9295285).

Reason: The donor-specific biochemical and glycopeptide measurements establish the defining first step of mucin-type O-GalNAc biosynthesis. Distinct acceptor and site preferences among GALNT1/2/3 do not weaken the shared process assignment. The soluble experimental proteins do not establish equivalent activity of every natural splice product.

Summary: The ARBA process assignment matches directly measured human O-GalNAc glycosylation.

Reason: The asserted process is the chemical mechanism demonstrated for human GALNT3: transfer of GalNAc onto protein serine/threonine acceptors. GO_REF:0000117 describes learned annotation rules, not a new assay; this particular claim is independently supported by human biochemical and cell experiments without requiring an unperformed audit of every rule condition.

Summary: GALNT3 participates directly in the curated mucin O-GalNAc pathway.

Reason: R-HSA-913709 contains the normal transfer reaction R-HSA-913675, whose catalyst set explicitly contains human GALNT3. This is chemical participation by the enzyme, independently supported by human mucin-peptide assays, rather than an inference from pathway necessity alone.

Summary: Manganese binding supports the catalytic machinery of human GALNT3 (PMID:9295285).

Reason: The purified human enzyme experiments support manganese-dependent GalNAc transfer, including failure of calcium or magnesium to replace manganese under the tested conditions. Retain manganese binding as a property of the catalytic core, without creating a separate core function. The specific human residue annotations at 277, 279 and 415 carry ECO:0000250|UniProtKB:H0ZAB5: their structural assignment is transferred from zebra finch GALNT3, not a direct human crystal observation. This separates the human functional cofactor evidence from the provenance of the residue-level model.

Summary: GALNT3 resides in Golgi cisternal membranes (PMID:9394011).

Reason: The human localization study reports GALNT3 in Golgi stacks, preferentially in their medial portion, using fractionation, immunofluorescence and immunoelectron microscopy. This supports the cisternal membrane location mapped from the UniProt subcellular vocabulary. The accessible abstract does not make this location exclusive, and no unverified typed edge to another membrane term is asserted.

Summary: Perinuclear localization is retained as a non-core aspect of GALNT3 Golgi residence (PMID:12506059).

Reason: The human ocular epithelial study directly probed GALNT3 with isoenzyme-specific monoclonal antibodies and reports its distribution in corneal and conjunctival epithelial layers. Together with independently established human GALNT3 Golgi localization, this supports retaining the curator's perinuclear assignment as a non-core location. The exact GALNT3 localization panel was not independently recovered. The abstract's explicit supranuclear sentence is not relabeled as a GALNT3 observation, and no paralog error is alleged; the judgment combines the positive target imaging with the established organelle context.

Summary: GALNT3 was detected in a human neural-stem-cell extracellular-vesicle fraction (PMID:18570454).

Reason: Original Table 2 identifies human GALNT3 through GI1617312, resolved by the official protein record to Q14435, in fraction 3 of HB1.F3 conditioned-medium vesicles. The fractions were separated by flow field-flow fractionation and examined by TEM; Table 1 reports fraction-3 particle diameters of 34.0 ± 1.40 nm. Although this protein has one matched peptide, the authors required a Mascot score above 50 and repeated detection across three shotgun analyses for single-peptide identifications. These observations support the reported vesicle-fraction association and its neural-stem-cell context. Retain it as non-core without treating technical repetition as independent biological replication or inferring membrane orientation, extracellular catalytic activity or vesicle biogenesis. Co-isolated material and the single-peptide identification remain limitations.