Figure 1.

Major synthesis and effector pathways of NO. Synthesis of NO primarily occurs through the action of NOS, although the conversion of dietary nitrogen containing compounds has also been proposed. Once produced, the function of NO can directly upregulate cGMP second messenger signaling pathways and directly modify the function of proteins through nitration. However, in the presence of other ROS such as superoxide, NO may form more reactive intermediates which can further alter the functionality of proteins. The balance of NO with ROS is critical to maintaining proper cellular function and the NO/ROS imbalance is implicated in the pathogenesis of many different diseases.