Figure 1 - Ceruloplasmin is a multicopper oxidase that is synthesized and secreted by the liver into the plasma.

Copper is incorporated into ceruloplasmin during synthesis and is essential for oxidase activity. Within the plasma, ceruloplasmin catalyzes the oxidation of the signaling molecule NO concomitantly with cupric (Cu²⁺) to cuprous (Cu¹⁺) reduction. Nitrite (NO₂^-) ions can therefore be used as a sink for NO production through reduction by deoxyhemoglobin, which allows for the mobilization of NO as a signaling molecule involved in hypoxic vasodilation and ischemia-reperfusion cytoprotection. In addition, nitrite acts independently as a signaling molecule necessary for cytoprotection and post-translational modifications such as iron nitrosylation and N-and S-nitrosation.