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Updated: Jul 10, 2026
09:43
Measurement of Heme Synthesis Levels in Mammalian Cells
Published on: July 9, 2015
Heme-hemopexin: a 'chronosteric' heme-protein
1Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Roma, Italy.
IUBMB Life
|October 31, 2007
Summary
Hemopexin (HPX) binds toxic heme and exhibits transient ligand-binding and enzymatic properties. This review explores HPX-heme
Area of Science:
- Biochemistry
- Protein Structure
- Heme Biology
Background:
- Hemopexin (HPX) is a plasma protein that scavenges and transports toxic heme to the liver.
- HPX is composed of two beta-propeller domains that bind heme in a pocket formed by the interdomain linker.
- The heme iron is coordinated by His213 and His266, forming a bis-histidyl complex.
Purpose of the Study:
- To review the ligand-binding and pseudo-enzymatic properties of the HPX-heme complex.
- To explore the potential of HPX-heme as a 'chronosteric' heme-protein.
Main Methods:
- Literature review of studies on Hemopexin (HPX) and its heme complex.
- Analysis of structural and functional data related to HPX-heme interactions.
- Comparison of HPX-heme properties with other heme-proteins.
Main Results:
- HPX-heme reversibly binds CO, (*)NO, and cyanide by detaching His213.
- O(2) induces oxidation of HPX-heme(II).
- HPX-heme(II) facilitates scavenging of (*)NO/O(2) and (*)NO/peroxynitrite, preventing low-density lipoprotein oxidation.
Conclusions:
- HPX functions not only as a heme carrier but also exhibits transient heme-based ligand-binding and pseudo-enzymatic activities.
- The unique properties suggest HPX-heme can be considered a 'chronosteric' heme-protein.
- HPX plays a crucial role in preventing heme-induced oxidative damage.
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