An immobilised enzyme.

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An immobilised enzyme is an enzyme literally that has been attached to a support that takes the form of small beads. The techniques for immobilisation vary.

  1. Chemical (covalent) attachment of the enzyme to a supporting material.
  2. Gel entrapment: the enzyme is mixed with gel-forming ingredients and when the gel forms the enzyme remains "trapped" in the gel matrix. The pores are large enough to let the substrate in, but not the enzyme out.
  3. Adsorption to various surfaces is sometimes used but because the attachment is not permanent this method is usually only used for scientific studies or for "disposable" enzymes. 
  4. Encapsulated in a compartment behind a semi-permeable (porous) membrane 
  5. Crosslinking of enzyme molecules 

The immobilised enzyme beads are added into a reaction tank and are recovered later by sedimentation or they are set up in a reactor column so that liquid flows continuously past the beads.  

The disadvantages of immobilisation are

  • losses of enzyme activity can occur during the making of the beads 
  • diffusion of substrates and products may be hampered by partitioning of the enzyme in the immobilised layer 
  • the enzyme may have a more constrained conformation in the immobilised state, giving it a lower catalytic activity 
  • may be a high initial investment for the immobilisation, compared to free enzyme 
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The advantages of immobilisation are

  • prevention of losses due to flushing away of enzyme 
  • a more stable enzyme 
  • the possibility to produce an enzymes with altered properties 

immobilised enzymes and cells, enzyme reactors, biosensors, use of enzymes and enzyme inhibitors for commercial and medical purposes, secondary plant metabolism.

Immobilisation can greatly effect the stability of an enzyme. If the immobilisation process introduces any strain into the enzyme, this is likely to encourage the inactivation of the enzymes under denaturing conditions (e.g. higher temperatures or extremes of pH). However where there is ...

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