Cu (II) Protoporphyrin IX does not inhibit heme oxygenase (the enzyme that catalyzes the conversion of heme to biliverdin in the heme degradation pathway) and is used as a negative control for Zn (II) Protoporphyrin (an inihibitor of heme oxygenase).  Heme oxygenase has been implicated in tumor cell resistance to chemotherapy¹, reduction of free radical formation² and inflammation³ and associated with vascular repair³.