Immobilized enzyme
Encyclopedia
An immobilized enzyme is an enzyme
that is 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 allows enzymes to 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.
, which are the following, listed in order of effectiveness:
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that is 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
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
or temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
. It also allows enzymes to 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
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
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 proteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
dissolveSolvationSolvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...
in the reaction, so workup can be much easier. Upon completion, reaction mixtures typically contain only solventSolventA solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
and reaction products. - Economical: The immobilized enzyme is easily removed from the reaction making it easy to recycle the biocatalyst.
- Stability: Immobilized enzymes typically have greater thermalThermal stabilityThermal stability is the stability of a molecule at high temperatures; i.e. a molecule with more stability has more resistance to decomposition at high temperatures....
and operational stabilityChemical stabilityChemical stability when used in the technical sense in chemistry, means thermodynamic stability of a chemical system.Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. This may be a dynamic equilibrium, where individual atoms...
than the soluble form of the enzyme.
Immobilization of an Enzyme
There are three different ways by which one can immobilise an enzymeEnzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
, which are the following, listed in order of effectiveness:
- 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 reactionChemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
, 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 alginateCalcium alginateCalcium alginate is a water-insoluble, gelatinous, cream coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate. Adding artificial flavours and colours creates a more tasty edible slime...
beads. However, this insoluble substances hinders the arrival of the substrate, and the exit of products. - Cross-linkageCross-linked enzyme aggregateIn biochemistry, a cross-linked enzyme aggregate is an immobilized enzyme prepared via crosslinking. They can be used as stereoselective industrial biocatalysts.-Background:Enzymes are proteins that catalyze chemical reactions...
: The enzyme is covalently bonded to a matrix through a chemical reactionChemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
. This method is by far the most effective method among those listed here. As the chemical reaction ensures that the binding site does not cover the enzyme's active siteActive siteIn biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...
, 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 glycolEthylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
) helps reduce the steric hindrance by the substrate in this case.
External links
- http://www.chiralvision.com/pdf/carrier-bound_enzymes_chiralvision.pdf Article on enzyme immobilization.