Key Difference – Enzyme vs Coenzyme
Chemical reactions convert one or more substrates into products. These reactions are catalyzed by special proteins called enzymes. Enzymes act as a catalyst for most reactions without being consumed. Enzymes are made from amino acids and have unique amino acid sequences composed of 20 different amino acids. Enzymes are supported by small non-protein organic molecules called cofactors. Coenzymes are one type of cofactors which help enzymes to perform catalysis. The key difference between enzyme and coenzyme is that enzyme is a protein which catalyzes the biochemical reactions while coenzyme is a non-protein organic molecule which helps enzymes to activate and catalyze the chemical reactions. Enzymes are macromolecules while coenzymes are small molecules.
CONTENTS
1. Overview and Key Difference
2. What is an Enzyme
3. What is a Coenzyme
4. Side by Side Comparison – Enzyme vs Coenzyme
5. Summary
What is an Enzyme?
Enzymes are biological catalysts of living cells. They are proteins composed of hundreds to millions of amino acids attached together like pearls on a string. Each enzyme has a unique amino acid sequence, and it is determined by a specific gene. Enzymes accelerate almost all the biochemical reactions in living organisms. Enzymes only influence the rate of the reaction, and their presence is essential to initiate the chemical conversion because activation energy of the reaction is lowered by enzymes. Enzymes change the rate of the reaction without being consumed or without changing the chemical structure. The same enzyme can catalyze the conversion of more and more substrates into products by showing the ability to catalyze the same reaction over and over again.
Enzymes are highly specific. A particular enzyme binds with a specific substrate and catalyzes a specific reaction. The specificity of the enzyme is caused by the shape of the enzyme. Each enzyme has an active site with a specific shape and functional groups for specific binding. Only the specific substrate will match the shape of the active site and bind with it. The specificity of the enzyme substrate binding can be explained by two hypothesis named lock and key hypothesis and induced fit hypothesis. Lock and key hypothesis indicate the match between enzyme and substrate is specific similar to a lock and a key. Induced fit hypothesis tells that the shape of the active site may change in order to fit the shape of the specific substrate similar to gloves fitting one’s hand.
Enzymatic reactions are affected by several factors such as pH, temperature, etc. Each enzyme has an optimum temperature value and pH value to work efficiently. Enzymes also interact with non-protein cofactors such as prosthetic groups, coenzymes, activators, etc. to catalyze biochemical reactions. Enzymes can be destroyed at high temperature or by high acidity or alkalinity because they are proteins.
Figure 01: Induced fit model of enzyme activity.
What is a Coenzyme?
Chemical reactions are aided by non-protein molecules called cofactors. Cofactors help enzymes to catalyze chemical reactions. There are different types of cofactors and coenzymes are one type among them. Coenzyme is an organic molecule which combines with an enzyme substrate complex and helps the catalysis process of the reaction. They are also known as helper molecules. They are made up of vitamins or derived from vitamins. Therefore, diets should contain vitamins which provide essential coenzymes for the biochemical reactions.
Coenzymes can bind with the active site of the enzyme. They bind loosely with the enzyme and aid the chemical reaction by providing functional groups needed for the reaction or by altering the structural conformation of the enzyme. Therefore, binding of the substrate become easy, and the reaction drives towards the products. Some coenzymes act as secondary substrates and become chemically altered at the end of the reaction, unlike enzymes.
Coenzymes cannot catalyze a chemical reaction without an enzyme. They help enzymes to become active and carry out their functions. Once the coenzyme binds with the apoenzyme, the enzyme becomes an active form of the enzyme called holoenzyme and initiates the reaction.
Examples of coenzymes are Adenosine triphosphate (ATP), Nicotinamide adenine dinucleotide (NAD), Flavin adenine dinucleotide (FAD), Coenzyme A, vitamins B1, B2, and B6, etc.
Figure 02: Cofactor binding with an apoenzyme
What is the difference between Enzyme and Coenzyme?
Enzyme vs Coenzyme |
|
| Enzymes are biological catalysts which accelerate chemical reactions. | Coenzymes are organic molecules which help enzymes to catalyze the chemical reactions. |
| Molecular Type | |
| All enzymes are proteins. | Coenzymes are non-proteins. |
| Alteration due to Reactions | |
| Enzymes are not altered due to the chemical reaction. | Coenzymes become chemically altered as a result of the reaction. |
| Specificity | |
| Enzymes are specific. | Coenzymes are not specific. |
| Size | |
| Enzymes are larger molecules. | Coenzymes are smaller molecules. |
| Examples | |
| Amylase, proteinase, and kinase are examples of enzymes. | NAD, ATP, coenzyme A, and FAD are examples of coenzymes. |
Summary – Enzyme vs Coenzyme
Enzymes catalyze chemical reactions. Coenzymes help enzymes to catalyze the reaction by activating enzymes and providing functional groups. Enzymes are proteins composed of amino acids. Coenzymes are not proteins. They are mainly derived from vitamins. This is the differences between enzymes and coenzymes.
Reference:
1. “Enzymes.” RSC. N.p., n.d. Web. 15 May 2017. <http://www.rsc.org/Education/Teachers/Resources/cfb/enzymes.htm>.
2. “Structural Biochemistry/Enzyme/Coenzymes.” Structural Biochemistry/Enzyme/Coenzymes – Wikibooks, open books for an open world. N.p., n.d. Web. 15 May 2017. <https://en.wikibooks.org/wiki/Structural_Biochemistry/Enzyme/Coenzymes>.
Image Courtesy:
1. “Induced fit diagram” By Created by TimVickers, vectorized by Fvasconcellos – Provided by TimVickers (Public Domain) via Commons Wikimedia
2. “Enzymes”By Moniquepena – Own work (Public Domain) via Commons Wikimedia