hemin

Hemin is protoporphyrin IX containing a ferric iron (Fe³⁺) ion with a coordinating chloride ligand.

Chemically, hemin differs from the related heme-compound hematin chiefly in that the coordinating ion is a chloride ion in hemin, whereas the coordinating ion is a hydroxide ion in hematin.{{cite journal | vauthors = Grenoble DC, Drickamer HG | title = The effect of pressure on the oxidation state of iron. 3. Hemin and hematin | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 61 | issue = 4 | pages = 1177–82 | date = December 1968 | pmid = 5249803 | pmc = 225235 | doi = 10.1073/pnas.61.4.1177 | bibcode = 1968PNAS...61.1177G | url = http://www.pnas.org/content/61/4/1177.full.pdf | doi-access = free }} The iron ion in haem is ferrous (Fe²⁺), whereas it is ferric (Fe³⁺) in both hemin and hematin.

Hemin is endogenously produced in the human body, for example during the turnover of old red blood cells. It can form inappropriately as a result of hemolysis or vascular injury. Several proteins in human blood bind to hemin, such as hemopexin and serum albumin.

A lyophilised form of hemin is used as a pharmacological agent in certain cases for the treatment of porphyria attacks, particularly in acute intermittent porphyria. Administration of hemin can reduce heme deficits in such patients, thereby suppressing the activity of delta-amino-levulinic acid synthase (a key enzyme in the synthesis of the porphyrins) by biochemical feedback, which in turn reduces the production of porphyrins and of the toxic precursors of heme. In such pharmacological contexts, hemin is typically formulated with human albumin prior to administration by a medical professional, to reduce the risk of phlebitis and to stabilize the compound, which is potentially reactive if allowed to circulate in free-form. Such pharmacological forms of hemin are sold under a range of trade names including the trademarks Panhematin{{Cite web|url=http://www.porphyriafoundation.com/content/panhematin-acute-porphyria|title=Panhematin for Acute Porphyria|website=American Porphyria Foundation|access-date=30 September 2017|archive-date=12 March 2018|archive-url=https://web.archive.org/web/20180312084311/http://www.porphyriafoundation.com/content/panhematin-acute-porphyria|url-status=dead}} and Normosang.{{Cite web|url=https://www.medicines.org.uk/emc/medicine/20795|title=Normosang |website=Electronic Medicines Compendium (eMC)}}

Hemin was first crystallized out of blood in 1853, by Ludwik Karol Teichmann. Teichmann discovered that blood pigments can form microscopic crystals. Thus, crystals of hemin are occasionally referred to as 'Teichmann crystals'. Hans Fischer synthesized hemin, for which he was awarded the Nobel Prize in Chemistry in 1930.{{Cite web|url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1930/fischer-lecture.pdf | first = Hans | last = Fischer | name-list-style = vanc |work = Nobel Lecture | title = On hemin and the relationships between hemin and chlorophyll | publisher = Nobel Prize Foundation}} Fischer's procedure involves treating defibrinated blood with a solution of sodium chloride in acetic acid.{{cite journal|title=Hemin | first = Hans | last = Fischer | name-list-style = vanc |journal=Org. Synth.|year= 1941|volume=21|page=53|doi=10.15227/orgsyn.021.0053}}

Hemin can be produced from hemoglobin by the so-called Teichmann test, when hemoglobin is heated with glacial acetic acid (saturated with saline). This can be used to detect blood traces.

Hemin is considered the "X factor" required for the growth of Haemophilus influenzae.{{cite book|title=Sherris medical microbiology: an introduction to infectious diseases| vauthors = Sherris JC, Ryan KJ, Ray CL |publisher=McGraw-Hill|year=2004|isbn=0-8385-8529-9|location=New York|pages=395}}

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• {{MeSH name|Hemin}}

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Category:Porphyrins

Category:Orphan drugs