Precursor to metabolite: Retinol to Tretinoin

Retinol is converted to Tretinoin by retinol / retinal dehydrogenase.

The pair

Retinol — Vitamin A; fat-soluble precursor to retinal for vision and retinoic acid for gene regulation.
Tretinoin — All-trans retinoic acid; topical acne drug and systemic differentiation therapy for APL.