The main difference between enzyme and coenzyme is that the enzyme is a protein which catalyzes a particular biochemical reaction inside the cell whereas the coenzyme is a non-protein molecule which carries chemical groups between enzymes.
Enzyme and coenzyme are two types of biomolecules which facilitate the occurrence of biochemical reactions in the cell. Enzymes do not chemically alter their structure during the reaction while coenzymes alter their structure during the reaction.
Key Areas Covered
1. What is an Enzyme
– Definition, Structure, Role in a Biochemical Reaction
2. What is a Coenzyme
– Definition, Structure, Role in a Biochemical Reaction
3. What are the Similarities Between Enzyme and Coenzyme
– Outline of Common Features
4. What is the Difference Between Enzyme and Coenzyme
– Comparison of Key Differences
Key Terms
Biological Catalyst, Coenzyme, Cofactor, Enzyme, Enzyme Activation
What is an Enzyme
An enzyme is a biological macromolecule made up of proteins. The main function of an enzyme is to catalyze a specific biochemical reaction inside the cell at body temperature and pH. Hence, enzymes are the biological catalysts on which all biological systems depend on. Thus, enzymes play a critical role in the maintenance of life.
Figure 1: Action of an Enzyme
Most enzymes are globular proteins with high molecular weights. Their ability to catalyze a specific biochemical reaction is one of the characteristic features of an enzyme. Moreover, they are active at a particular temperature and pH. They also require the binding of a cofactor to the active site in order to activate the apoenzyme to the holoenzyme, the active form of the enzyme. Some inorganic cofactors include Mg2+, Fe2+, Zn2+, and Mn2+ while small organic molecules that act as cofactors are called coenzymes. Significantly, only a small quantity of an enzyme is required for catalysis. The action of the enzyme is mainly regulated by the allosteric mechanisms in which the product formed by the enzyme inhibit the enzyme, inhibiting the formation of more products.
Figure 2: Action of a Cofactor
There are six types of enzymes based on the type of reaction they catalyze. They are oxidoreductases, transferases, lyases, hydrolases, ligases, and isomerases. Apart from the action inside the body, enzymes are used in the food industry for the fermentation as well as in medicine to promote wound healing, kill pathogens, diagnose diseases, etc.
What is a Coenzyme
A coenzyme is a small organic molecule that acts as a cofactor. It binds to the enzymes, assisting the function of the enzyme. While facilitating the enzymatic action, coenzymes serve as intermediate carriers of electrons, specific atoms or functional groups between biochemical reactions. Some of the functional groups transferred by coenzymes are hydride ions, hydrogen atoms, methyl groups, and acyl groups. Once bound to a chemical group, the structure of the coenzyme is changed. Therefore, coenzymes can be considered as the second substrate to the enzyme. Hence, they are called co-substrates. Coenzymes need to regenerate in order to participate in the reaction again and again.
Figure 3: Involvement of Coenzymes in the Citric Acid Cycle
Some coenzymes include NAD (nicotine adenine dinucleotide), NADP (nicotine adenine dinucleotide phosphate), FAD (flavin adenine dinucleotide) (Vit.B2), CoA (coenzyme A), CoQ (coenzyme Q), thiamine (vitamin B1), pyridoxine (vitamin B6), biotin, folic acid, etc.
Similarities Between Enzyme and Coenzyme
- Enzyme and coenzyme are essential components of the biochemical reactions that occur in the body.
- They facilitate the occurrence of biochemical reactions.
- Both are biomolecules.
Difference Between Enzyme and Coenzyme
Definition
An enzyme refers to a substance produced by living organisms to act as a biological catalyst to bring about a specific biochemical reaction while a coenzyme refers to a non-protein compound necessary for the functioning of an enzyme. This explains the main difference between enzyme and coenzyme.
Size
Enzymes are large molecules while coenzymes are small molecules.
Structure
The structure is another difference between enzyme and coenzyme. Enzymes are mainly globular proteins while coenzymes are organic molecules.
Function
One other important difference between enzyme and coenzyme is their function. Enzymes serve as biological catalysts while coenzymes bind to the active site of the enzyme, activating it.
Change
Furthermore, enzymes do not change their structure during the reaction while coenzymes change their structure during the reaction by binding to functional groups released from the reaction.
Specificity
Moreover, enzymes are very specific to the reactions they catalyze while coenzymes are less specific.
Conclusion
An enzyme is a globular protein that serves as a biological catalyst. But, a coenzyme is a small, organic molecule, which binds to the enzyme to activate it. Enzymes do not change their structure during the reaction while coenzymes change their structure by binding to the functional groups. The main difference between enzyme and coenzyme is their structure and function.
Reference:
1. Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. The Central Role of Enzymes as Biological Catalysts. Available Here
2. Berg JM, Tymoczko JL, Stryer L. Biochemistry. 5th edition. New York: W H Freeman; 2002. Section 8.6, Vitamins Are Often Precursors to Coenzymes. Available Here
Image Courtesy:
1. “Induced fit diagram” By Created by TimVickers, vectorized by Fvasconcellos – Provided by TimVickers (Public Domain) via Commons Wikimedia
2. “OSC Microbio 08 01 ApoHolo” By CNX OpenStax – https://cnx.org/contents/[email protected] (CC BY 4.0) via Commons Wikimedia
3. “Citric acid cycle with aconitate 2” By Narayanese, WikiUserPedia, YassineMrabet, TotoBaggins – http://biocyc.org/META/NEW-IMAGE?type=PATHWAY&object=TCA. Image adapted from :Image:Citric acid cycle noi.svg|(uploaded to Commons by wadester16) (CC BY-SA 3.0) via Commons Wikimedia
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