Protoporphyrin IX

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Protoporphyrin IX
3D model (JSmol)
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  • InChI=1S/C34H34N4O4/c1-7-21-17(3)25-13-26-19(5)23(9-11-33(39)40)31(37-26)16-32-24(10-12-34(41)42)20(6)28(38-32)15-30-22(8-2)18(4)27(36-30)14-29(21)35-25/h7-8,13-16,35,38H,1-2,9-12H2,3-6H3,(H,39,40)(H,41,42)/b25-13-,26-13-,27-14-,28-15-,29-14-,30-15-,31-16-,32-16- ☒N
  • InChI=1/C34H34N4O4/c1-7-21-17(3)25-13-26-19(5)23(9-11-33(39)40)31(37-26)16-32-24(10-12-34(41)42)20(6)28(38-32)15-30-22(8-2)18(4)27(36-30)14-29(21)35-25/h7-8,13-16,35,38H,1-2,9-12H2,3-6H3,(H,39,40)(H,41,42)/b25-13-,26-13-,27-14-,28-15-,29-14-,30-15-,31-16-,32-16-
  • CC\1=C(/C/2=C/C3=N/C(=C\C4=C(C(=C(N4)/C=C\5/C(=C(C(=N5)/C=C1\N2)C=C)C)C=C)C)/C(=C3CCC(=O)O)C)CCC(=O)O
Molar mass 562.658 g/mol
Density 1.27 g/cm3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Protoporphyrin IX is an organic compound, specifically a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like hemoglobin and chlorophyll. It is a deeply colored solid that is not soluble in water. The name is often abbreviated as PPIX.

Protoporphyrin IX contains a porphine core, a tetrapyrrole macrocycle with a marked aromatic character. Protoporphyrin IX is essentially planar, except for the N-H bonds that are bent out of the plane of the rings, in opposite (trans) directions.[1]

The general term protoporphyrin refers to porphine derivatives that have the outer hydrogen atoms in the four pyrrole rings replaced by four methyl groups −CH
(M), two vinyl groups −CH=CH
(V), and two propionic acid groups −CH
(P). The Roman numeral "IX" indicates that these chains occur in the circular order MV-MV-MP-PM around the outer cycle. (The numbering of the variants is traditional and not entirely systematic.)


  • When UV light is shone on the compound, it can floresce with a bright red color.
  • It Is also the component in egg shells that give them their characteristic brown color.
Floresence Due To UV Light In Egg Shells.png

Natural occurrence[edit]

The compound is encountered in nature in the form of complexes where the two inner hydrogen atoms are replaced by a divalent metal cation. When complexed with an iron(II) (ferrous) cation Fe2+, the molecule is called heme. Hemes are prosthetic groups in some important proteins. These heme-containing proteins include hemoglobin, myoglobin, and cytochrome c. Complexes can also be formed with other metal ions, such as zinc.[2]


The compound is synthesized from acyclic precursors via a mono-pyrrole (porphobilinogen) then a tetrapyrrole (a porphyrinogen, specifically uroporphyrinogen III). This precursor is converted to protoporphyrinogen IX, which is oxidized to protoporphyrin IX.[2] The last step is mediated by the enzyme protoporphyrinogen oxidase.

protoporphyrin IX synthesis from protoporphyrinogen-IX

Protoporphyrin IX is an important precursor to biologically essential prosthetic groups such as heme, cytochrome c, and chlorophylls. As a result, a number of organisms are able to synthesize this tetrapyrrole from basic precursors such as glycine and succinyl-CoA, or glutamic acid. Despite the wide range of organisms that synthesize protoporphyrin IX, the process is largely conserved from bacteria to mammals with a few distinct exceptions in higher plants.[3][4][5]

In the biosynthesis of those molecules, the metal cation is inserted into protoporphyrin IX by enzymes called chelatases. For example, ferrochelatase converts the compound into heme B (i.e. Fe-protoporphyrin IX or protoheme IX). In chlorophyll biosynthesis, the enzyme magnesium chelatase converts it into Mg-protoporphyrin IX.

Described metalloprotoporphyrin IX derivatives[edit]

The following metals are known to from Heme-like complexes when coordinated to PPX:

These compounds follow the naming convention [metal]-protoporphyrin IX, or protoporphyrin IX containing [metal].

Protoporphyrin IX reacts with iron salts in air to give the complex FeCl(PPIX).[19]

Palepron is the disodium salt of protoporphyrin IX.[20]

See also[edit]


  1. ^ Winslow S. Caughey, James A. Ibers (1977). "Crystal and Molecular Structure of the Free Base Porphyrin, Protoporphyrin IX Dimethyl Ester". J. Am. Chem. Soc. 99: 6639–6645. doi:10.1021/ja00462a027.CS1 maint: uses authors parameter (link)
  2. ^ a b Paul R. Ortiz de Montellano (2008). "Hemes in Biology". Wiley Encyclopedia of Chemical Biology. John Wiley & Sons. doi:10.1002/9780470048672.wecb221.
  3. ^ A. R. Battersby; C. J. R. Fookes; G. W. J. Matcham; E. McDonald (1980). "Biosynthesis of the pigments of life: formation of the macrocycle". Nature. 285: 17–21. doi:10.1038/285017a0. PMID 6769048.
  4. ^ F. J. Leeper (1983). "The biosynthesis of porphyrins, chlorophylls, and vitamin B12". Natural Product Reports. 2: 19–47. doi:10.1039/NP9850200019.
  5. ^ G. Layer; J. Reichelt; D. Jahn; D. W. Heinz (2010). "Structure and function of enzymes in heme biosynthesis". Protein Science. 19: 1137–1161. doi:10.1002/pro.405. PMC 2895239. PMID 20506125.
  6. ^ PubChem. "Mg-protoporphyrin IX". Retrieved 2021-04-15.
  7. ^ PubChem. "Cobalt protoporphyrin IX". Retrieved 2021-04-16.
  8. ^ PubChem. "Ti-Protoporphyrin IX". Retrieved 2021-04-15.
  9. ^ PubChem. "Cr-Protoporphyrin". Retrieved 2021-04-15.
  10. ^ PubChem. "Ni-Protoporphyrin". Retrieved 2021-04-15.
  11. ^ PubChem. "Protoporphyrin IX containing MN". Retrieved 2021-04-15.
  12. ^ PubChem. "Cu-Protoporphyrin". Retrieved 2021-04-15.
  13. ^ PubChem. "Protoporphyrin IX containing ZN". Retrieved 2021-04-15.
  14. ^ PubChem. "Tin protoporphyrin IX". Retrieved 2021-04-15.
  15. ^ PubChem. "Cd-Protoporphyrin". Retrieved 2021-04-15.
  16. ^ PubChem. "Pt-Mesoporphyrin". Retrieved 2021-04-15.
  17. ^ PubChem. "3-[18-(2-Carboxyethyl)-8,13-bis(ethenyl)-3,7,12,17-tetramethyl-22,23-dihydroporphyrin-2-yl]propanoic acid;gold". Retrieved 2021-04-16.
  18. ^ PubChem. "3-[18-(2-Carboxyethyl)-8,13-bis(1-hydroxyethyl)-3,7,12,17-tetramethyl-22,23-dihydroporphyrin-2-yl]propanoic acid;silver". Retrieved 2021-04-16.
  19. ^ Chang, C. K.; DiNello, R. K.; Dolphin, D. (1980). "Iron Porphines". Inorg. Synth. Inorganic Syntheses. 20: 147. doi:10.1002/9780470132517.ch35.
  20. ^ PubChem. "Protoporphyrin disodium". Retrieved 2021-04-15.