TH
TH tyrosine hydroxylase — the molecular target that 2 compounds in the wiki act on.
In one line: The factory enzyme that builds dopamine, your motivation-and-drive chemical.
TH (tyrosine hydroxylase) is the rate-limiting enzyme that manufactures dopamine (and downstream, noradrenaline) — the brain chemicals behind motivation, focus, and alertness. "Rate-limiting" just means it's the slowest step, so it sets how much dopamine you can make.
Supplying the raw material (the amino acid tyrosine) helps most when you're depleted — under stress, cold, or sleep loss — by giving this factory more to work with. Some compounds (like bromantane) work by increasing the amount of this enzyme, so you build more dopamine over time rather than just releasing what you have.