P4HA1
P4HA1 prolyl hydroxylase — the molecular target that 1 compounds in the wiki act on.
In one line: The enzyme that builds collagen — and it can't work without vitamin C.
P4HA1 is a key enzyme in making collagen, the scaffolding of your skin, tendons, and bone. Crucially, it needs vitamin C to function — which is the whole reason severe vitamin-C deficiency (scurvy) makes the body fall apart.
The practical takeaway: taking collagen with vitamin C isn't optional if you want to actually build connective tissue, because this enzyme literally can't finish the job without the vitamin.