[HEMH_HUMAN] Defects in FECH are the cause of erythropoietic protoporphyria (EPP) [MIM:177000]. Porphyrias are inherited defects in the biosynthesis of heme, resulting in the accumulation and increased excretion of porphyrins or porphyrin precursors. They are classified as erythropoietic or hepatic, depending on whether the enzyme deficiency occurs in red blood cells or in the liver. EPP is a form of porphyria marked by excessive protoporphyrin in erythrocytes, plasma, liver and feces, and by widely varying photosensitive skin changes ranging from a burning or pruritic sensation to erythema, edema and wheals.
[HEMH_HUMAN] Catalyzes the ferrous insertion into protoporphyrin IX.
Ferrochelatase (protoheme ferrolyase, EC 126.96.36.199) is the terminal enzyme in heme biosynthesis and catalyzes the insertion of ferrous iron into protoporphyrin IX to form protoheme IX (heme). Due to the many critical roles of heme, synthesis of heme is required by the vast majority of organisms. Despite significant investigation of both the microbial and eukaryotic enzyme, details of metal chelation remain unidentified. Here we present the first structure of the wild-type human enzyme, a lead-inhibited intermediate of the wild-type enzyme with bound metallated porphyrin macrocycle, the product bound form of the enzyme, and a higher resolution model for the substrate-bound form of the E343K variant. These data paint a picture of an enzyme that undergoes significant changes in secondary structure during the catalytic cycle. The role that these structural alterations play in overall catalysis and potential protein-protein interactions with other proteins, as well as the possible molecular basis for these changes, is discussed. The atomic details and structural rearrangements presented herein significantly advance our understanding of the substrate binding mode of ferrochelatase and reveal new conformational changes in a structurally conserved pi-helix that is predicted to have a central role in product release.
A pi-helix switch selective for porphyrin deprotonation and product release in human ferrochelatase.,Medlock AE, Dailey TA, Ross TA, Dailey HA, Lanzilotta WN J Mol Biol. 2007 Nov 2;373(4):1006-16. Epub 2007 Aug 23. PMID:17884090
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↑ Medlock AE, Dailey TA, Ross TA, Dailey HA, Lanzilotta WN. A pi-helix switch selective for porphyrin deprotonation and product release in human ferrochelatase. J Mol Biol. 2007 Nov 2;373(4):1006-16. Epub 2007 Aug 23. PMID:17884090 doi:10.1016/j.jmb.2007.08.040