## TXNDC12
- **UniProt:** O95881 (ERp18/ERp19/ERp16/hTLP19) · **batch:** proteostasis-batch-2026-06-11 · **review status:** COMPLETE
- **PN placement:** `ER proteostasis | Folding enzyme | Protein disulfide isomerases` ; **PN-node mapping:** group=mapped, scope=ok_for_propagation_to_go, GO=GO:0003756 protein disulfide isomerase activity (class/branch=no_mapping). Projection goa_status=new_to_goa.
- **Consistency:** Largely consistent with a caveat on the projected term. Review, notes, and deep research describe a small soluble ER-lumen thioredoxin-superfamily oxidoreductase with an unusual CGAC active site (Cys66/Cys69) that "catalyzes formation, reduction, and isomerization of disulfide bonds" (PMID:18628206; PMID:12761212), redox potential ~−165 mV, EDEL-retained. So it does have isomerase-type chemistry (unlike TXNDC11). GOA MF terms are GO:0019153 protein-disulfide reductase (glutathione) activity and GO:0015035 protein-disulfide reductase activity; the review core MF is GO:0015035. The PN projects GO:0003756 (isomerase).
- **PN story / NEW pressure:** Lower NEW pressure than TXNDC11 — TXNDC12 already HAS catalytic MF terms in GOA (GO:0015035, GO:0019153; verified goa.tsv), accepted in the review. PN claims GO:0003756 is new_to_goa, which is literally true (isomerase term specifically is absent), and the literature does report isomerization activity, so GO:0003756 is defensible-but-redundant given the existing reductase terms. Per OLS, GO:0003756 (isomerase) and GO:0015035 (reductase) are siblings, so GO:0003756 would ADD an activity facet rather than refine an existing one. Conclusion: already substantially captured (reductase); GO:0003756 is a defensible minor ADD, not an over-reach, since isomerase activity is experimentally reported.
- **Mapping strategy:** Acceptable. Catalytic, canonical PDI-family member that genuinely belongs in the "Protein disulfide isomerases" group (in contrast to TXNDC11). Group GO:0003756 projection is reasonable here. No node change needed.
- **Evidence alignment:** PN mapping-only. Review key refs: IDA PMID:12761212 (ERp18 characterization), PMID:18628206 (ERp16, isomerization + anti-apoptotic role), PMID:39696500 (vWF/thrombosis, non-core). Isomerization activity in PMID:18628206 supports the PN GO:0003756 projection.
- **Verdict:** Consistent; catalytic MF already in GOA (reductase) — PN GO:0003756 isomerase projection is a defensible, literature-supported minor ADD rather than core-missing or over-reach.