| Cofactor (biochemistry) |
Article Index for Cofactor |
Information AboutCofactor (biochemistry) |
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An Enzyme without a cofactor is referred to as an apoenzyme, and the completely active enzyme (in addition to the cofactor) is called a holoenzyme. Apoenzyme + cofactor <=> Holoenzyme Metal Ion s are common cofactors. In Nutrition , the list of essential Trace Element s reflects their role as cofactors. This list includes Manganese , Iron , Cobalt , Nickel , Copper , Zinc , and Molybdenum . Other organisms require additional metals, such as Vanadium and Tungsten . The study of these cofactors falls under the area of Bioinorganic Chemistry . Some cofactors undergo chemical changes during the course of a reaction, undergoing Reduction or Oxidation . Nonetheless, as a Catalyst , cofactors return to their original state in the course of the catalytic cycle. They are not consumed. In this respect, cofactors differ from Substrate s or Coenzyme s. In many cases, the cofactor includes both an inorganic and organic components. One diverse set of examples are the Heme proteins, which consists of a Porphyrin ring coordinated to Iron . Cofactors vary in their location and the tightness of their binding to the host enzyme. When bound tightly to the enzyme, cofactors are called Prosthetic Group s. Loosely-bound cofactors typically associate in a similar fashion to enzyme Substrate s. These are better described as Coenzyme s, which are organic substances that directly participate as substrates in an enzyme reaction. Vitamin s can serve as precursors to coenzymes (e.g. vitamins B1 , B2 , B6 , B12 , Niacin , Folic Acid ) or as coenzymes themselves (e.g. Vitamin C ). EXTERNAL LINKS |
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