BACKGROUND
Enzyme Inhibitors
Enzyme inhibitors are substances that change how an enzyme catalyses, slowing down or, in some cases, stopping catalysis as a result. Competitive, non-competitive, and substrate inhibition are the three main forms of enzyme inhibition.
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When the substrate and a chemical that looks like the substrate are both given to the enzyme, competitive inhibition happens. Why inhibition happens can be explained by the “lock-key theory” of enzyme catalysts.
Non-competitive inhibitors are substances that, when added to an enzyme, change it so that it is unable to accept a substrate. Instances of substrate inhibition might happen when there is an abundance of the substrate.
Reversible inhibition is the transient loss of enzyme activity brought on by the non-covalent attachment of inhibitors to the enzyme proteins. Reversible inhibitors can either entirely or partially restore enzyme activity when they are removed physically, such as by dialysis. Competitive, uncompetitive, non-competitive, and mixed inhibition are all types of reversible inhibition.
Urea and guanidine are well known for their ability to denaturate proteins by severing intramolecular hydrogen bonds. According to theory, linkages that contribute to the tertiary structure of enzyme molecules are eliminated when catalytic activity is lost in the presence of urea. Reversible denaturation, which is the process of restoring structural and catalytic capabilities after the denaturant has been removed, is typically seen as proof that the hydrogen bonds that had broken had been repaired.
The current studies have shown that milk xanthine oxidase exhibits an immediate inhibition in the presence of low concentrations of urea, which is easily overridden by dilution. A kinetic analysis showed that urea inhibits this enzyme in a formally competitive manner.
Twenty-one other enzymes have been evaluated in a similar manner for their susceptibility to urea inhibition, with the nature of the inhibition in each case being defined. The findings have shown unique patterns of urea inhibition that are thought to have implications for each case’s process of enzyme-substrate complex formation. In an effort to better comprehend the relevance of the competitive inhibition by urea of enzymes, many situations have been explored.
Enzyme inhibitors are crucial in the pharmaceutical and healthcare sectors. A fundamental understanding of inhibitor function is helpful to pharmacologists when creating novel therapeutic drugs.
Artificial inhibitors include pesticides like malathion, herbicides like glyphosate, and disinfectants like triclosan. Other artificial enzyme inhibitors are used as nerve agents in chemical warfare because they block the enzyme acetylcholinesterase, which breaks down acetylcholine.
Some nanoparticles can bind proteins, and this dynamic interaction can change both the native structure of the attached protein and the physicochemical characteristics of the nanoparticle. Particle size and surface-functional group features are just two of the variables that affect how nanoparticle-protein interactions behave. These interactions may be advantageous for drug transport and cellular imaging applications, but they also carry the risk of harm because they may inhibit or even denaturate non-target proteins.
REQUIREMENTS
- Test tube
- Starch
- Amylase
- Iodine
- Spectrophotometer
- Spectrophotometer cuvettes
- Distilled water
- Beaker
PROCEDURE
- Take 5-10 test tube, add 1-2 ml of iodine solution to all tubes,
- Label tube as 0 min, 2 min, 4 min and so on,
- Prepare starch-amylase mixture,
- Add 2 ml of starch-amylase mixture immediately to 0 min label tube,
- After every interval of time add 2 ml of starch-amylase mixture to respective tube,
- Measured the absorbance of all sample in between 250-300 nm using a spectrophotometer,
- Plot a graph by using an absorbance value at X-axis and time at Y-axis.
CONCLUSION
By observing the plotted graph, we successfully learn the effect of inhibitors on enzyme activity.
REFERENCES
- K.V. Rajagopalan, Irwin Fridovich and Philip Handler, “Competitive inhibition of enzyme activity by urea”, The Journal of Biological Chemistry, vol. 236, no 4, April 1961.
- Tyson J. Maccormack, Rhett J. Clark, Michael K.M. Dang, Guibin MA, Joel A. Kelly, Jonathan G. C. Veinot & Greg G. Goss, “Inhibition of enzyme activity by nanomaterials: potential mechanisms and implications for nanotaxicity testing”, Nanotoxicology, August 2012.
- Hong Cai, Mohammad Al-Fayez, Richard G. Tunstall, Sharon Platton, Peter Greaves, William P. Steward & Andreas J. Gescher, “The rice bran constituent tricin potently inhibits cyclooxygenase enzymes and interferes with intestinal carcinogenesis in Apcmin mice”, Molecular cancer Therapeutics, September 2005.
- https://prezi.com/2rzxwakmyzcb/amylase-enzyme-activity-and-action-of-inhibitors/
Also read:
- Biochemical Test (IMViC reactions)
- Study of bacterial morphology by acid-fast staining (Ziehl and Neelsen staining method)
- Mutagenesis with Ethidium bromide/NTG or EMS
- Protein denaturation by egg albumin method (in vitro)
- Estimation of white blood cell count (TLC/ Total Leucocyte Count)
- Analgesic activity study of drugs by tail-flick method
FAQs:
Yes, Invertase-Sucrose mixture is use instead of starch amylase.
An enzyme’s ability to be stimulated, inhibited, or turned off by a chemical is known as an allosteric site. It differs from the active site of an enzyme, which is where substrates bind.
Reversible inhibition reactions come in four different varieties. The four types of inhibition are competitive, non-competitive, uncompetitive, and mixed.
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