What is the Difference Between Free and Immobilized Enzymes

The key difference between free and immobilized enzymes is that free enzymes are enzymes that are not bound to any substrate, whereas immobilized enzymes cannot move from one place to another.

For some important functions in our body like digestion, respiration, and excretion, we need chemicals that can accelerate the process. These chemicals are known as enzymes. These enzymes have important roles in all living things, and thereby govern all biological processes.

Enzymes are proteins. They have catalytic capabilities. Usually, the metabolic processes inside cells are carried out by enzymes. Sometimes there are a set of enzymes we require for a particular process. In the catalytic process, the substance on which the enzyme acts is named the substrate. An enzyme can convert a substrate into one or more other substances named as products.

CONTENTS

1. Overview and Key Difference
2. What are Free Enzymes
3. What are Immobilized Enzymes
4. Free vs Immobilized Enzymes in Tabular Form
5. Summary

What are Free Enzymes?

Free enzymes are enzymes that are not bound to any substrate molecule. A catalytic reaction that involves an enzyme progresses through the binding of the enzyme with a substrate. There is an active site on an enzyme that allows the substrate to bind with it. Therefore, catalysis depends mainly on the activity of amino acid side chains that are arranged in the active site. The complex of enzyme-substrate is named as the intermediate product of catalysis reaction.

More importantly, the substrate should have a matching shape to the active site of the enzyme; otherwise, it will not bind. Therefore, the substrate has a specific structure that allows them to fit in a particular enzyme. When the enzyme provides the substrate with a surface to bind, the activation energy of the reaction is reduced. After the binding of the substrate, it forms the intermediate product, and this step of intermediate production is named the transition state. At this step, bond breaking and bond formations occur where the chemical structure of the substrate changes while the structure of the enzyme remains constant. After the products have formed, these products have a shape that unfit the active site of the enzyme and therefore, the products are released from the enzyme. Thereafter, we can observe the free enzyme that can bind with other substrates again to give similar products. Likewise, the catalytic cycle continues.

What are Immobilized Enzymes?

Immobilized enzymes are enzymes that are attached to an inert material. These enzymes cannot move from one place to another. Usually, the material to which the enzyme is bound is inert and insoluble, e.g. calcium alginate produced from a mixture of sodium alginate solution and enzyme solution in the presence of calcium chloride. Immobilization of an enzyme can provide increased resistance to pH changes and temperature changes. It also lets the enzyme be attached to a single place until the end of the reaction. Therefore, we can easily separate the enzyme from the products to use them again in a reaction.

There are many commercial uses of immobilized enzymes due to convenience (a small amount of the enzyme is enough to perform a reaction), economy (easy to recycle the biocatalyst), and stability (typically, this type of enzyme has a great thermal and operational stability than free enzyme).

We can use different methods to immobilize an enzyme which includes affinity-tag binding, adsorption onto glass, alginate beads or a matrix, entrapment, cross-linkage method, covalent bonding, etc.

What is the Difference Between Free and Immobilized Enzymes?

Free and immobilized enzymes are two different phases of enzymes. The key difference between free and immobilized enzymes is that free enzymes are enzymes that are not bound to any substrate, whereas immobilized enzymes cannot move from one place to another.

The below tabulation lists more differences between free and immobilized enzymes.

Summary – Free vs Immobilized Enzymes

Enzymes are proteins. There are various different enzymes that are useful in biological processes. An enzyme binds with a substrate to give products. When there is no substrate bound, the enzyme is in a “free” state. Moreover, we can immobilize an enzyme for commercial purposes. The key difference between free and immobilized enzymes is that free enzymes are enzymes that are not bound to any substrate, whereas immobilized enzymes cannot move from one place to another.

Reference:

1. “Enzymes – Structure, Classification, and Function.” BYJUS, 22 Feb. 2021.

Image Courtesy:

1. “Glucosidase enzyme” By Thomas Shafee – Own work (CC BY-SA 4.0) via Commons Wikimedia
1. “Enzymes immobilised in alginate gel” By Tess Watson – Flickr (CC BY 2.0) via Commons Wikimedia