|MadSci Network: Biochemistry|
You have recognized heme (or haeme), a metalloprotein, as an important biochemical structure. It is, indeed, present in hemoglobin, chlorophyll and cytochromes. It can be found in mitochondria, chloroplasts, ER and other places in the cell. The electrochemistry of the metal present in the protein is critical to its function. The tremendous value is the ability to interact in oxidation-reduction reactions and transport oxygen, both between tissues and within cells. Redox reactions and the biological transfer of electrons are essential for energy production in living organisms. Interest in the structure of heme is the reason that myoglobin was the first protein whose structure was described and the finding of tertiary and quaternary structures. These configurations give the molecule three-dimensional shape and allow the molecule to twist and turn to provide access to the heme groups.
Hemes are present in every Kingdom, bacteria, protists, fungi and plants and animal. The prevalence of this pathway suggests that the gene that encodes the protein is ancient. The different functions are probably new uses for a protein structure whose gene was already present.
Biosynthesis of the heme of hemoglobin and chlorophyll both start with the porphyrin ring structure. The pathways diverge where the metal ion is added, iron for hemoglobin, magnesium for chlorophyll. A mutation in the pathway to hemoglobin results in the genetic disease porphyria.
Here is an interesting site to look at:
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