Protoporphyrin IX is a tetrapyrrole containing 4 methyl, 2 propionic and 2 vinyl side chains that is a metabolic precursor for hemes, cytochrome c and chlorophyll. It belongs to the porphyrin family, which are a class of tetrapyrroles. It is the iron-free form of hemin and amphiphilic in nature.

Protoporphyrin-9 is the key porphyrin in animal and plant cells, presenting a precursor scaffold for heme sites and other metal domains contained in metalloproteins. Iron is introduced to the porphyrin to generate heme, the primary oxygen-binding moiety found in proteins. Protoporphyrin-9 as heme is incorporated into hemoglobin, catalase, peroxidase, and certain cytochrome enzymes. Introduction of magnesium into Protoporphyrin-9 and subsequent transformations generates chlorophyll, the main light energy-gathering pigment in plants necessary for photosynthesis. Protoporphyrin-9 is also demonstrated to activate guanylate cyclase, indicating that cellular levels of Protoporphyrin-9 and heme may serve to regulate guanylate cyclase activity and tissue cyclic GMP levels. λex 402 nm, 409 nm λem 625 nm, 633 nm

Reference

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