The key difference between cholinesterase and pseudocholinesterase is that cholinesterase is an enzyme mainly found in red cells and neurons that hydrolyzes released acetylcholine while pseudocholinesterase is a type of cholinesterase found in serum, plasma, liver, pancreas, heart, and other tissues that hydrolyzes released acetylcholine.
Cholinesterase is an enzyme that aids the nervous system to work the way it normally should. Certain toxic chemicals in the environment can interfere with the function of this enzyme and affect the nervous system. Examples of these chemicals are organophosphates and carbamates, which are most often found in insecticides used in fields. Cholinesterases hydrolyze the released acetylcholine at central and peripheral sites. There are two types of cholinesterase: acetylcholinesterase or true cholinesterase and pseudocholinesterase.
CONTENTS
1. Overview and Key Difference
2. What is Cholinesterase
3. What is Pseudocholinesterase
4. Similarities – Cholinesterase and Pseudocholinesterase
5. Cholinesterase vs. Pseudocholinesterase in Tabular Form
6. FAQ – Cholinesterase and Pseudocholinesterase
7. Summary – Cholinesterase vs. Pseudocholinesterase
What is Cholinesterase?
The enzyme cholinesterase catalyzes the hydrolysis of choline-based esters (such as acetylcholine). This reaction allows a cholinergic neuron to return to its resting state after activation. For example, when a muscle contracts, acetylcholine at a neuromuscular junction triggers a contraction. However, for the muscle to relax afterward, the acetylcholine must be broken down by a cholinesterase enzyme.
The main type of cholinesterase for this purpose is acetylcholinesterase, primarily found in chemical synapses and red blood cell membranes. The other type is pseudo-cholinesterase or butyrylcholinesterase, mainly found in blood plasma.
Figure 01: Cholinesterase
What is Pseudocholinesterase?
Pseudocholinesterase (PCHE) is normally present in serum, plasma, liver, pancreas, heart, and other tissues. It is also known as butrylcholinesterase (BuChE) or plasmacholinesterase. This plasma enzyme is produced in the liver and is responsible for the metabolism of the common anesthesia drugs, succinylcholine and mivacurium, as well as ester local anesthetics, which include cocaine.
Furthermore, individuals with normal functioning of this enzyme can rapidly metabolize succinylcholine and mivacurium, leading to a short duration of action of these drugs. However, with an inherited deficiency of this enzyme, it is unable to metabolize succinylcholine and mivacurium to the same degree. This ultimately causes prolonged neuromuscular paralysis and a disorder called pseudocholinesterase deficiency.
What are the Similarities Between Cholinesterase and Pseudocholinesterase?
- Cholinesterase and pseudocholinesterase are two associated enzymes.
- This is because pseudocholinesterase is a type of cholinesterase.
- Both are able to convert hydrolysis of choline-based esters.
- Organophosphates inhibit both.
- They are extremely important for nerve function.
What is the Difference Between Cholinesterase and Pseudocholinesterase?
Acetylcholinesterase is usually found in large amounts in red blood cells and neurons, whereas pseudocholinesterase (PCHE) or butrylcholinesterase (BuChE) is present in serum, plasma, liver, pancreas, heart, and other tissues. Thus, this is the key difference between cholinesterase and pseudocholinesterase. Both these enzymes hydrolyze acetylcholine. Furthermore, cholinesterase is produced by either muscles or the liver. On the other hand, pseudocholinesterase is produced only by the liver.
The infographic below presents the differences between cholinesterase and pseudocholinesterase in tabular form for side-by-side comparison.
FAQ: Cholinesterase and Pseudocholinesterase
What is the role of pseudocholinesterase?
Pseudocholinesterase is an enzyme that breaks down (metabolizes) drugs known as choline esters.
What are examples of pseudocholinesterase?
Some examples of pseudocholinesterase are procaine, tetracaine, benzocaine, and cocaine.
Where is pseudocholinesterase primarily found?
Pseudocholinesterase is primarily found in the liver.
Summary – Cholinesterase vs. Pseudocholinesterase
The main two types of cholinesterase are acetylcholinesterase (true cholinesterase) and pseudocholinesterase. Cholinesterase, or true cholinesterase, is mainly found in red cells and neurons. Pseudocholinesterase is a type of cholinesterase that also hydrolyzes released acetylcholine, which is only found in serum, plasma, liver, pancreas, heart, and other tissues. These two enzymes differ in their substrate preferences as well. So, this summarizes the difference between cholinesterase and pseudocholinesterase.
Reference:
1. “Cholinesterase – An Overview.” ScienceDirect Topics.
2. “Pseudocholinesterase.” Statpearls – NCBI Bookshelf.
Image Courtesy:
1. “Pralidoxime Mechanism” By Kilinkie – Own work (CC BY 3.0) via Commons Wikimedia