Science: Uncovering and Discovering

Enzymes are immobilized by attaching to or enclosing in inert support materials. Immobilization can be brought about by one of several procedures like physical entrapment, ionic or covalent bonding, and encapsulation. Properties of immobilized enzymes are very different from those in free solution. This depends, to a great extent, on the method of immobilization and the nature of support material. E.g., some harsh immobilization processes can denature the enzyme, leading to reduction in its activity.

Further, the support material creates a new microenvironment, which can affect enzyme activity in a variety of ways. E.g., enzyme may undergo conformational change due to interactions with functional groups on the support. These changes, at times, lead to stabilization of enzymes. Thus, appropriate immobilization procedures can be used to increase the shelf life of enzymes. The pH optimum of the enzyme may also change due to the new microenvironment. This is due to the change in the ionization of amino acids at the active site. Desired pH optimum changes can be brought about by selecting appropriate support matrices.

Another important effect that support matrix can impose is the steric hindrance of substrate diffusion. This is advantageous in some cases, where the enzyme can be saved from the action of proteolytic enzymes in solution. The proteases are excluded from the support matrix. However, the disadvantage is that limitation on substrate diffusion leads to lower substrate concentration and higher product concentration in the vicinity of the enzyme as compared to that in solution. This leads to inhibition of enzyme activity and reduction in the rate of reaction. The apparent Km of the enzyme also increases, leading to inefficient catalysis.

Posted on Monday, October 20th, 2008 at 2:26 am Categorized as:General

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