What is the Difference Between Cholinesterase and Pseudocholinesterase

The main difference between cholinesterase and pseudocholinesterase is that cholinesterase occurs in large amounts in red blood cells and neurons, whereas pseudocholinesterase occurs in the liver, serum, plasma, heart, pancreas, and other tissues. 

Cholinesterase and pseudocholinesterase are two enzymes that hydrolyze different compounds. 

Key Areas Covered

1. What is Cholinesterase
– Definition, Facts, Features
2. What is Pseudocholinesterase
– Definition, Facts, Features
3. Similarities Between Cholinesterase and Pseudocholinesterase
– Outline of Common Features
4. Difference Between Cholinesterase and Pseudocholinesterase
– Comparison of Key Differences
5. FAQ – Cholinesterase and Pseudocholinesterase
– Answers to frequently asked questions

Key Terms  

Cholinesterase, Pseudocholinesterase

What is Cholinesterase

Cholinesterase is the enzyme responsible for the hydrolysis of acetylcholine released by the central and peripheral nervous system. True cholinesterase and pseudocholinesterase are the two types of cholinesterase. Another name for the true cholinesterase is acetylcholinesterase (AChE). It occurs in neurons and red blood cells in large amounts. The primary location of acetylcholinesterase is postsynaptic neuromuscular junctions, especially in muscles and nerves. The primary function of acetylcholinesterase is to break down acetylcholine (ACh) immediately. Here, acetylcholine is a naturally-occurring neurotransmitter. Acetic acid and choline are the breakdown products of acetylcholine.

Figure 2: ACHE

Furthermore, the role of acetylcholinesterase is to terminate neuronal transmission, which in turn removes the signaling between synapses. However, acetylcholine disperses and activates nearby neurons. Critically, Organophosphates inhibit acetylcholinesterase, an essential component of nerve agents and pesticides.

What is Pseudocholinesterase

Pseudocholinesterase is a serine hydrolase primarily produced in the liver. It catalyzes the hydrolysis of choline esters, most prominently succinylcholine and mivacurium. Other names of pseudocholinesterase include plasma cholinesterase, serum cholinesterase, acetylcholine acetylhydrolase, and butyrylcholinesterase (BuChE). The ratio of butyrylcholinesterase to acetylcholinesterase is 1000 to 1. Therefore, the primary cholinesterase form in the human body is butyrylcholinesterase. Also, the primary function of butyrylcholinesterase is to affect the activity of neurons, specifically within the hippocampus, amygdala, thalamus, and different deep layers of the cerebral cortex.

Figure 2: BCHE

Moreover, a butyrylcholinesterase deficiency increases the sensitivity to succinylcholine and mivacurium-like choline ester-based muscle relaxant medications. 

Similarities Between Cholinesterase and Pseudocholinesterase

• Cholinesterase and pseudocholinesterase are two enzymes involved in the hydrolysis of compounds.
• They are essential to remove the action of other enzymes.  

Difference Between Cholinesterase and Pseudocholinesterase

Definition

Cholinesterase refers to an enzyme, especially acetylcholinesterase, which hydrolyses choline esters. In contrast, pseudocholinesterase refers to a plasma enzyme produced in the liver responsible for metabolizing common anesthesia drugs, succinylcholine, mivacurium, and ester local anesthetics, including cocaine.

Occurrence

Cholinesterase occurs in large amounts in red blood cells and neurons, while pseudocholinesterase occurs in the liver, serum, plasma, heart, pancreas, and other tissues.

Types

Acetylcholinesterase and pseudocholinesterase are the two types of cholinesterase, while pseudocholinesterase is a type of cholinesterase.

Concentration

Acetylcholinesterase occurs in low concentrations, while butyrylcholinesterase occurs in low concentrations. 

Function

Cholinesterase hydrolyzes acetylcholine released by the central and the peripheral nervous system, while pseudocholinesterase hydrolyzes choline esters, succinylcholine, and mivacurium. 

FAQ: Cholinesterase and Pseudocholinesterase

What is the difference between plasma cholinesterase and pseudocholinesterase? 

Plasma cholinesterase is a type of pseudocholinesterase responsible for the breakdown of succinylcholine in the plasma. Meanwhile, pseudocholinesterase hydrolyzes choline esters. 

What is pseudocholinesterase also known as? 

Pseudocholinesterase deficiency or butyrylcholinesterase deficiency is a rare, inherited disease caused by the deficiency of pseudocholinesterase produced by the liver.   

What is the function of pseudocholinesterase? 

Pseudocholinesterase breaks down choline esters such as succinylcholine, a part of anesthesia used to relax muscles during medical procedures. Therefore, pseudocholinesterase deficiency causes the muscles to rest for too long time after getting succinylcholine. 

Conclusion

In brief, cholinesterase and pseudocholinesterase are two enzymes in the body. Cholinesterase occurs in large amounts in red blood cells and neurons. Also, it is responsible for hydrolyzing acetylcholine released by the central and peripheral nervous system. In comparison, pseudocholinesterase occurs in the liver, serum, plasma, heart, pancreas, and other tissues. However, it hydrolyzes choline esters, most prominently succinylcholine and mivacurium. Therefore, the main difference between cholinesterase and pseudocholinesterase is their occurrence and function.  

References:

1. Trang A, Khandhar PB. Physiology, Acetylcholinesterase. [Updated 2023 Jan 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
2. Benner A, Lewallen NF, Sadiq NM. Biochemistry, Pseudocholinesterase. [Updated 2022 Sep 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.

Image Courtesy:

1. “PBB Protein ACHE image” By ProteinBoxBot at English Wikipedia – Own Work (Public Domain) via Commons Wikimedia
2. “Protein BCHE PDB 1p0i” By Emw (CC BY SA 3.0) via Commons Wikimedia