Containing Coenzymes Are Frequently Involved in Redox Reactions

Iron-Containing Coenzymes Are Frequently Involved in Redox Reactions 

Iron as a cofactor in catalysis is receiving increasing attention. The most common oxidation states of iron are Fe2+ and Fe3+. Iron complexes are nearly all octahedral, and practically all are paramagnetic (as a result of unpaired electrons in the 3d orbital). The most common form of iron in biological systems is heme. Heme groups (Fe2+) and hema-tin (Fe3+) most frequently involve a complex with protoporphyrin IX (fig. 10.19). They are the coenzymes (prosthetic 

Heme proteins exhibit characteristic visible absorption spectra as a result of protoporphyrin IX their spectra differ depending on the identities of the lower axial ligand donated by the protein and the oxidation state of the iron as well as 

Structure of protoporphyrin IX. This coenzyme acts in conjunction with a number of different enzymes involved in oxidation and reduction reactions. 

Heme coenzymes, iron-sulfur clusters, flavin coenzymes, and nicotinamide coenzymes cooperate in multienzyme systems to catalyze the chemically remarkable hy-droxylations of hydrocarbons such as steroids (chapter 20). In these hydroxylation systems, the heme proteins constitute a family of proteins known as cytochrome P450, named for the wavelength corresponding to the most intense absorption band of the carbon monoxide-liganded heme, an inhib- 

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Ascorbic Acid Is Required to Maintain the Enzyme that Forms Hydroxyproline Residues in Collagen Vitamin B12 Coenzymes Are Associated with Rearrangements on Adjacent Carbon Atoms Iron-Containing Coenzymes Are Frequently Involved in Redox Reactions Metal Cofactors Lipid-Soluble Vitamins... 

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