Protoporphyrin IX is an intermediate in the Heme synthesis pathway and is formed from Protoporphyrinogen III in a reaction catalyzed by the enzyme Protoporphyrin III oxidase. It plays an important role in living organisms as a precursor for other critical compounds like hemoglobin and chlorophyll. It can form heme when added to ferrous iron in the presence of the enzyme ferrochelatase and has been found to activate guanylate cyclase and has been found to induce apoptosis in HeLa cells.
1) Bednarz, N., J. Zawacka-Pankau, et al. (2007). “Protoporphyrin IX induces apoptosis in HeLa cells prior to photodynamic treatment.” Pharmacol Rep 59(4): 474-9
2) Strand, A., T. Asami, et al. (2003). “Chloroplast to nucleus communication triggered by accumulation of Mg-protoporphyrin IX.” Nature 421(6918): 79.