Calcitriol biosynthesis from calciol is going

GO:0036378 is replaced by a redefined GO:1901755 vitamin D3 biosynthetic process

AI Gene Review · projects/CALCITRIOL_BIOSYNTHESIS_OBSOLETION · 2026

Bottom line

  • GO is obsoleting GO:0036378 and pointing it at GO:1901755, once that term's primary output is changed from calciol to calcitriol.
  • 24 curated annotations on 5 CYP enzymes move. Four enzymes catalyse an activation step; CYP24A1 inactivates, so its successor term needs a check.
  • Scoped, not started. Only human CYP27A1 has a review here, and its row already sits on GO:1901755.

The pathway and the two terms

Why a clean replaced_by works

  • The two hydroxylations are the only enzymatic steps in MetaCyc PWY-6076; the first step is photochemical.
  • Upstream already added the PWY-6076 xref and changed has_primary_output to CHEBI:17823 calcitriol.
  • So GO:1901755 now covers exactly what GO:0036378 covered.
  • No mappings (InterPro2GO, UniRule, keywords) point at GO:0036378, so there is no electronic fallout to triage.

Who carries the annotations

Status and next steps

  1. Wait for the replaced_by step in go-ontology#32077; go-annotation#6449 shows BHF-UCL and UniProt done.
  2. Review CYP27B1 first (just fetch-gene human CYP27B1), then CYP2R1.
  3. Treat CYP3A4 (minor 25-hydroxylase) and CYP24A1 (inactivator) as edge cases; report CYP24A1 upstream if a catabolic term fits better.

Existing review: genes/human/CYP27A1/CYP27A1-ai-review.yaml (GO:1901755 row KEEP_AS_NON_CORE)

Read more: projects/CALCITRIOL_BIOSYNTHESIS_OBSOLETION.md