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Enzyme induction and inhibition

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It gives the brief information to the students regarding the enzyme induction and inhibition process and their mechanism.

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Enzyme induction and inhibition

  1. 1. ENZYME INDUCTIONANDINHIBITION Dr. B. Manjari Assistant professor
  2. 2.  Enzyme is a biological catalyst, i.e. a substance that alters the rate of a reaction without itself becoming permanently altered by its participation in the reaction.  The ability of an enzyme (particularly a proteinaceous enzyme) to catalyze a reaction can be altered by binding various small molecules to it,  sometimes at its active site, and sometimes at a site distant from the active site.  Usually these alterations involve a reduction in the enzyme's ability to accelerate the reaction; less commonly, they give rise to an increase in the enzyme's ability to accelerate a reaction.
  3. 3. Inhibitors:  Inhibitors are chemicals that reduce the rate of enzymatic reactions,  They are usually specific and they work at low concentrations,  They block the enzymatic action but they do not usually destroy them.
  4. 4.  Inhibitors are broadly be classified as reversible and irreversible.  Irreversible inhibitors bind permanently to their target enzyme, often via a covalent bond that influences catalysis.  Irreversible inhibition can be rarely seen i.e, they are not as common as Reversible inhibition.  Inhibitors can be washed off the body by the dialysis process.
  5. 5.  They are of 2 categories based on the distinction related to the location and characteristics of the inhibition.  Many inhibitors act at the active site by binding in the same way that one of the substrates or intermediates binds. Thus if the inhibitor is present, it is competing for the active site of the enzyme- Competitive inhibition.  If the inhibitor binds more tightly to the active site than the substrate does, it is an effective competitive inhibitor, if it binds less strongly, it's a poor competitive inhibitor.
  6. 6.  If instead the inhibitor binds at a site on the enzyme that is distinct from the active site, then its presence will induce a conformational change in the protein.  This reduces the ability of the enzyme to facilitate the reaction.  This kind of inhibitor does not interfere with the binding of the substrate(s) to the active site, but it does interfere with catalysis.  Such a competitor is termed non-competitive, since it isn't competing for the same site as the substrate.
  7. 7.  Uncompetitive inhibitors are those that bind to a site distinct from the active site, but only in the presence of bound substrate.  When they bind, they reduce the reaction velocity, because we convert some molecules of the enzyme-substrate complex into the nonproductive enzyme-substrate-inhibitor form.  Mixed inhibitors bind in a way that is reflective of some of the properties of a competitive and a noncompetitive, or a noncompetitive and an uncompetitive, inhibitor.  Most commonly, these are inhibitors that bind at a site distant from the active site, but in binding they influence substrate binding as well as turnover.
  8. 8.  The process of increasing the amount or the activity of a protein – Enzyme induction.  A homeostatic mechanism for regulating enzyme production in a barrier organ, such as the liver, intestine, kidney.  The inducer usually combines with and deactivates/activates a regulatory protein which leads to increased gene expression.  Many of the enzymes involved in drug metabolism may be up-regulated by exposure to drugs and environmental chemicals leading to increased rates of metabolism.

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