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An immobilised enzyme.

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Introduction

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. ...read more.

Middle

This is primarily due to the physical prevention of the large conformational changes within the protein structure which generally precede its inactivation. Many successful covalent immobilisation processes involve an initial freely-reversible stage, where the covalent links are allowed to form, break and re-form until an unstrained covalently-linked structure is created, in order to stabilise the resultant immobilised enzyme. Additional stabilisation is derived by preventing the enzyme molecules from interacting with each other, and the protection that immobilisation affords towards proteolytic and microbiological attack. This latter effect is due to a combination of diffusional difficulties and the camouflage to enzymic attack produced by the structural alterations. In order to achieve maximum stabilisation of the enzymes, the surfaces of the enzyme and support should be complementary with the formation of many unstrained covalent or non-covalent interactions. Often, however, this factor must be balanced against others, such as the cost of the process, the need for a specific support material, and ensuring that the substrates are not sterically hindered from diffusing to the active site of the immobilised enzyme in order to react at a sufficient rate. ...read more.

Conclusion

In order to eliminate wastage and improve productivity the enzyme and product can be separated during the reaction. The enzyme can be imprisoned allowing it to be reused but also preventing contamination of the product - this is known as immobilisation. Unstable enzymes may be immobilised by being attached to or located within an insoluble support, therefore the enzyme is not free in solution. Once attached, an enzyme's stability is increased, possibly because its ability to change shape is reduced. Advantages of immobilisation Disadvantages of immobilisation 1. Easier to separate enzyme and products 1. Immobilisation may alter shape of enzyme 2. Allows catalysis in unfavourable media 2. May alter catalytic ability 3. Increases stability and can be manipulated easily 3. Enzyme may become detached 4. Allows continuous production/enzyme used for longer 4. Expensive 5. Enzyme can be recovered and reused 6. Enzyme does not contaminate product/no purification required Enzymes are proteins, and their function is determined by their complex structure. The reaction takes place in a small part of the enzyme called the active site, while the rest of the protein acts as "scaffolding". ...read more.

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