How is Nitric Oxide Produced in the Human Body?
Nitric oxide is produced in the human body by a group of enzymes known as nitric oxide synthases (NOS).
These enzymes convert the amino acid L-arginine into NO through a series of biochemical reactions.
Description of the Nitric Oxide Synthases (NOS) Process
NOS Enzymes Activation
There are three types of NOS enzymes (neuronal (nNOS or NOS1), inducible (iNOS or NOS2), and endothelial (eNOS or NOS3)) and they are typically activated in response to various cellular signals. For example, eNOS is typically activated by physical forces such as blood flow shear stress or by biochemical signals like insulin.
Conversion Process
Once activated, NOS enzymes facilitate the conversion of the amino acid L-arginine into nitric oxide (NO) and L-citrulline. This is a multi-step process that involves the transfer of electrons from NADPH, another molecule, through the enzyme to L-arginine. The enzyme also uses oxygen during this process.
Release and Utilization
Once produced, NO diffuses across membranes and affects nearby cells. It is a short-lived molecule and is rapidly converted into other compounds, so its effects are generally localized to the area where it is produced.