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Renin Angiotensin Mechanism.

Coenzymes–Structure and biochemical function.

 

Introduction:

  • Enzymes break down complex molecules and combine them to form simpler molecules, which are used by the body or excreted as waste material.

  • A cofactor can be needed if enzymes are unable to function alone in these reactions.

  • Holoenzymes or active enzymes, are complexes made up of two parts: a protein or apoenzyme and cofactors.

  • Proteins or apoenzymes cannot function alone; they need a cofactor to function. 

  • Activators, which are usually cations, can be cofactors. 

  • Coenzymes, which are non-protein compounds, are normally required for enzyme catalysis. Being complex, they prevent the separation of enzyme complex components.

Coenzyme - 

  • For an enzyme to catalyze a chemical reaction, it requires a particular molecule called a coenzyme.

  • Commonly, phosphorylated derivatives of water soluble vitamins are the main sources of coenzymes.

  • Coenzymes act by binding to the active sites of enzymes (apoenzymes). 

  • Coenzymes are mainly responsible for transporting electrons between the reactants in reaction chains.

    • e.g.  FAD, NAD, and NADP.

  • All three coenzymes play a role in oxidation and hydrogen transfer. 

  • Coenzymes are commonly referred to as co-substrates because they bind to the enzyme alongside the substrate at the start of a chemical reaction and alter the enzyme at the end. 

  • Coenzymes bind to enzymes before other substrates; hence they are called coenzymes. In addition, coenzymes are transformed again into their original forms by other enzymes in the cell. 

  • Cofactors and coenzymes are nutrients, such as vitamins and minerals. 

  • The breakdown of coenzymes involves vitamin and mineral cofactors. As a result, maintaining an adequate dietary intake of trace elements is critical for energy production. 

Biochemical Functions of Coenzymes:

  1. Vitamins as coenzymes - 

  • Retinoic acid is a metabolite of vitamin A that functions as a gene regulator and, thus, is important for cell growth. 

  • The enzymes that move -CO2 groups (g-carboxylases) require vitamin K as a coenzyme, it is crucial for the coagulation of blood.

  1. Minerals as cofactors and catalysts- 

  • A mineral can sometimes also act as a cofactor.

  • An enzyme or its substrate cannot be incorporated into minerals that act as catalysts. 

  • Their function is to increase the speed of the biochemical reaction between the enzyme and the substrate. 

  • Magnesium, manganese, selenium, and molybdenum are minerals that act as cofactors. 

  • For certain non-enzymatic proteins, minerals like cobalt, iodine, calcium, and phosphorus have the role of cofactors. 

  • Cofactors like copper, zinc, and iron are involved in both enzymatic and non-enzymatic processes.

Commonly Asked Questions:

  1. What are coenzymes and cofactors? Discuss their biochemical roles.

  2. Define coenzymes and cofactors with examples.
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