🎀Cofactors, coenzymes, and prosthetic groups 🎀

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Sofia

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  • Cofactors and Coenzymes are non-protein components needed for an enzyme to function
  • An organic cofactor is a coenzyme
  • Inorganic cofactors are obtained via the diet as minerals, including iron, calcium, chloride, and zinc ions
  • Amylase contains a chloride ion that is necessary for the formation of s correctly shaped active site. This is an example of an inorganic cofactor.
  • Many coenzymes are derived from vitamins ( a class of organic molecule found in the diet). For example, vitamin B3 is used to synthesise NAD; a coenzyme responsible for the transfer of hydrogen atoms between molecules involved in respiration. NADP (derived from vitamin B3) plays a similar role in photosynthesis. Another example is vitamin B5 which is used to make coenzyme A which is essential in the breakdown of fatty acids and carbohydrates in respiration.
  • Prosthetic groups are cofactors that are tightly bound to and form a permanent feature of the protein. For example, zinc ions form an important part of the structure of carbonic anhydrase which is necessary for the metabolism of CO2
  • Many enzymes are produced in an inactive form known as inactive precursor enzymes, particularly enzymes that can cause damage within the cells producing them or to the tissues where they are released or enzymes whose action needs to be controlled and only activated under certain conditions.
  • Precursor enzymes often need to undergo a change in shape (to their active site) to be activated. This can be achieved by the addition of a cofactor. Before the cofactor is added, the precursor protein is called an apoenzyme. Once the cofactor is added and the enzyme is activated it is called a holoenzyme.
  • Sometimes the change in the tertiary structure of the in the inactive precursor enzyme is brought about by the action of another enzyme. In some cases a change in conditions, pH or temp, results in a change in the tertiary structure and activates the precursor enzyme. These types of precursor enzymes are called zymogens or proenzymes.