NOS3
NOS3 endothelial nitric oxide synthase — the molecular target that 2 compounds in the wiki act on.
In one line: The enzyme that makes nitric oxide, the gas that widens your blood vessels.
NOS3 (also called eNOS) is the enzyme in your blood-vessel walls that produces nitric oxide — a gas signal that tells the vessel to relax and widen. Wider vessels mean more blood flow, more oxygen to your muscles, a better "pump" in the gym, and lower blood pressure.
Supplements like citrulline feed this enzyme more raw material so it can make more nitric oxide. Beetroot takes a shortcut, delivering nitric oxide through a separate route. And erectile-dysfunction drugs work further downstream, stopping the "widen" signal from being broken down.
This is one of the most useful systems for endurance athletes and for heart health — and it's the reason a pre-workout gives you that full, vascular feeling.