immobilized enzyme

WordNet

1. make defenseless (同)immobilise
2. cause to be unable to move; "The sudden storm immobilized the traffic" (同)immobilise
3. convert (assets) into fixed capital (同)immobilise
4. hold as reserve or withdraw from circulation; of capital (同)immobilise
5. any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/07/12 20:00:40」(JST)

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Enzymes immobilised in beads of alginate gel

An immobilized enzyme is an enzyme attached to an inert, insoluble material—such as calcium alginate (produced by reacting a mixture of sodium alginate solution and enzyme solution with calcium chloride). This can provide increased resistance to changes in conditions such as pH or temperature. It also lets enzymes be held in place throughout the reaction, following which they are easily separated from the products and may be used again - a far more efficient process and so is widely used in industry for enzyme catalysed reactions. An alternative to enzyme immobilization is whole cell immobilization.

Commercial use

Immobilized enzymes are very important for commercial uses as they possess many benefits to the expenses and processes of the reaction of which include:

• Convenience: Minuscule amounts of protein dissolve in the reaction, so workup can be much easier. Upon completion, reaction mixtures typically contain only solvent and reaction products.
• Economy: The immobilized enzyme is easily removed from the reaction making it easy to recycle the biocatalyst. This is particularly useful in processes such as the production of Lactose Free Milk, as the milk can be drained from a container leaving the enzyme (Lactase) inside ready for the next batch.
• Stability: Immobilized enzymes typically have greater thermal and operational stability than the soluble form of the enzyme.

In the past, biological washing powders and detergents contained many proteases and lipases that broke down dirt. However, when the cleaning products contacted human skin, they created allergic reactions. This is why immobilization of enzymes are important, not just economically.

Immobilization of an Enzyme

There are various ways by which one can immobilize an enzyme:

• Affinity-tag binding: Enzymes may be immobilized to a surface, e.g. in a porous material, using non-covalent or covalent Protein tags. This technology has been established for protein purification purposes, and has recently been applied for biocatalysis applications by EziG™ with the His-tag. This technique is the only one generally applicable, and can be performed without prior enzyme purification with a pure preparation as the result. Porous glass and derivatives thereof are used, where the porous surface can be adapted in terms of hydrophobicity to suit the enzyme in question.
• Adsorption on glass, alginate beads or matrix: Enzyme is attached to the outside of an inert material. In general, this method is the slowest among those listed here. As adsorption is not a chemical reaction, the active site of the immobilized enzyme may be blocked by the matrix or bead, greatly reducing the activity of the enzyme.
• Entrapment: The enzyme is trapped in insoluble beads or microspheres, such as calcium alginate beads. However, this insoluble substances hinders the arrival of the substrate, and the exit of products.
• Cross-linkage: Enzyme molecules are covalently bonded to each other to create a matrix consisting of almost only enzyme. The reaction ensures that the binding site does not cover the enzyme's active site, the activity of the enzyme is only affected by immobility. However, the inflexibility of the covalent bonds precludes the self-healing properties exhibited by chemoadsorbed self-assembled monolayers. Use of a spacer molecule like poly(ethylene glycol) helps reduce the steric hindrance by the substrate in this case.
• Covalent bond: The enzyme is bound covalentely to an insoluble support (such as silica gel). This approach provides the strongest enzyme/support interaction, and so the lowest protein leakage during catalysis.

Immobilization of a Substrate for Enzymatic Reactions

Another widely used application of the immobilization approach together with enzymes has been the enzymatic reactions on immobilized substrates. This approach facilitates the analysis of enzyme activities and mimics the performance of enzymes on e.g. cell walls.

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English Journal

• Quantification of l-lysine in cheese by a novel amperometric biosensor.

• Ciriello R1, Cataldi TR2, Crispo F3, Guerrieri A4.
• Food chemistry.Food Chem.2015 Feb 15;169:13-9. doi: 10.1016/j.foodchem.2014.07.141. Epub 2014 Aug 7.
• Lysine quantification in cheese by a novel, highly selective amperometric biosensor is reported. Based on l-lysine-α-oxidase immobilized by co-crosslinking onto Platinum (Pt) electrodes modified by overoxidized polypyrrole, the sensor proved almost specific to lysine, sensitive and stable. The pure
• PMID 25236192

• Sensitive and selective detection of thrombin by using a cyclic peptide as affinity ligand.

• Zhao Q1, Gao J2.
• Biosensors & bioelectronics.Biosens Bioelectron.2015 Jan 15;63:21-5. doi: 10.1016/j.bios.2014.07.010. Epub 2014 Jul 10.
• Here we describe a sensitive assay for thrombin by using a high binding-affinity cyclic peptide against thrombin as affinity ligand. The cyclic peptide is immobilized on the magnetic beads or microplates to selectively capture thrombin. The enriched thrombin then catalyzes the cleavage of a substrat
• PMID 25048449

Japanese Journal

• Immobilization of feruloyl esterases on magnetic nanoparticles and its potential in production of ferulic acid

• Journal of bioscience and bioengineering 120(3), 330-334, 2015-09
• NAID 40020593930

• Enhancement of immobilized lipase activity by design of polymer brushes on a hollow fiber membrane

• Journal of bioscience and bioengineering 120(3), 257-262, 2015-09
• NAID 40020593822

Related Links

• Enzyme immobilization: an overview on techniques and ...

Adsorption Enzyme adsorption results from hydrophobic interactions and salt linkages where either the support is bathed in enzyme for physical adsorption or the enzyme is dried on electrode surfaces. Adsorbed ...

• Immobilized Enzymes - Scribd - Read books, audiobooks ...

What is an Immobilized Enzyme? The term "immobilized" means unable to move or stationary. And that is exactly what an immobilized enzyme is: an enzyme that is physically attached to a solid support over which a substrate is ...

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