Cited by 493Porphyrin Metabolism and DisordersHemoglobin structure and functionPorphyrin and Phthalocyanine Chemistry

Biosynthesis of heme in mammals

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Ajioka, Richard S., Phillips, John D., Kushner, James P.·2006·Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

Abstract

Most iron in mammalian systems is routed to mitochondria to serve as a substrate for ferrochelatase. Ferrochelatase inserts iron into protoporphyrin IX to form heme which is incorporated into hemoglobin and cytochromes, the dominant hemoproteins in mammals. Tissue-specific regulatory features characterize the heme biosynthetic pathway. In erythroid cells, regulation is mediated by erythroid-specific transcription factors and the availability of iron as Fe/S clusters. In non-erythroid cells the pathway is regulated by heme-mediated feedback inhibition. All of the enzymes in the heme biosynthetic pathway have been crystallized and the crystal structures have permitted detailed analyses of enzyme mechanisms. All of the genes encoding the heme biosynthetic enzymes have been cloned and mutations of these genes are responsible for a group of human disorders designated the porphyrias and for X-linked sideroblastic anemia. The biochemistry, structural biology and the mechanisms of tissue-specific regulation are presented in this review along with the key features of the porphyric disorders.

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Crossref · 10.1016/j.bbamcr.2006.05.005

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  • PpIX is produced by aromatization of protoporphyrinogen IX by PPOX and has fluorescent and photosensitizing properties.

    “Protoporphyrinogen IX crosses the mitochondrial inner membrane and is aromatized by protoporphyrinogen oxidase (PPOX) to produce PpIX, a porphyrin metabolite with fluorescent and photosensitizing properties.”

    From 5-Aminolevulinic Acid as a Theranostic Agent for Tumor Fluorescence Imaging and Photodynamic Therapy (2023) · cites this paper as [8]

    Section 1.3 states that protoporphyrinogen IX is oxidized by PPO to protoporphyrin IX (PpIX) and that the resulting porphyrin is fluorescent. The Introduction links porphyrin fluorescence to photosensitivity. The paper does not say that protoporphyrinogen IX crosses the inner mitochondrial membrane before this reaction; section 1.3 places PPO on the membrane’s outer surface. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • Heme biosynthesis ends with insertion of ferrous iron into PpIX by ferrochelatase to form heme.

    “Heme biosynthesis ends in the mitochondrial matrix where ferrous iron (Fe2+) is inserted into the tetrapyrrole core of PpIX by ferrochelatase (FECH) to form heme [8].”
  • Heme biosynthesis in mammalian cells involves eight enzymes, four in the cytoplasm and four in the mitochondrion.

    “Heme biosynthesis in mammalian cells is a finely tuned process that involves eight enzymes with four in the cytoplasm and four in the mitochondrion [8], as shown in Figure 1.”
  • ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent.

    “As a porphyrin precursor, ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent.”
  • Conjugation of eight ALA molecules yields protoporphyrin IX (PpIX) and finally leads to formation of heme.

    “Conjugation of eight ALA molecules yields protoporphyrin IX (PpIX) and finally leads to formation of heme.”

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Authors
Ajioka, R. S., Phillips, J. D., & Kushner, J. P.
Affiliations
University of Utah (US)
Corresponding author
Kushner, James P.
Venue
Biochimica et Biophysica Acta (BBA) - Molecular Cell Research
Publisher
Elsevier BV
Published
2006-07
Volume
1763
Issue
7
Pages
723-736
ISSN
0167-4889 (ISSN-L)
OpenAlex
W2143881989
Cited by
493
References
108
Citations by year
2026: 25 · 2025: 17 · 2024: 18 · 2023: 21 · 2022: 28 · 2021: 39 · 2020: 36 · 2019: 24 · 2018: 29 · 2017: 34 · 2016: 32 · 2015: 31 · 2014: 25 · 2013: 20 · 2012: 18
FWCI
1.40
Type
journal article
Language
en
Open access
Locations
  • Biochimica et Biophysica Acta (BBA) - Molecular Cell Research (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health (5r01dk020503-32)
  • National Institute of Diabetes and Digestive and Kidney Diseases (DK-20503, DK 062106, R01-DK020503)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Porphyrin Metabolism and Disorders
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Hemoglobin structure and function
  • Physical Sciences › Materials Science › Materials Chemistry › Porphyrin and Phthalocyanine Chemistry
Keywords
heme biosynthesis, ferrochelatase, protoporphyrin IX, erythroid cells, iron availability, iron-sulfur clusters, enzyme crystal structure, porphyria, X-linked sideroblastic anemia, tissue-specific gene regulation, heme proteins
MeSH terms
Animals, Ferrochelatase, Heme, Mammals, Models, Molecular, Protein Conformation, Crystallography, X-Ray

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