What is the Difference Between Uridine and Pseudouridine

The main difference between uridine and pseudouridine is that in uridine, uracil is attached by a nitrogen-carbon glycosidic bond, whereas in pseudouridine, uracil is attached by a carbon-carbon glycosidic bond. 

Uridine and pseudouridine are two isomeric nucleosides that occur in nature. Also, pseudouridine is cellular RNA’s most common form of RNA modification.  

Key Areas Covered

1. What is Uridine
– Facts, Features, Behaviour
2. What is Pseudouridine
– Facts, Features, Behaviour
3. Similarities Between Uridine and Pseudouridine
– Outline of Common Features
4. Difference Between Uridine and Pseudouridine
– Comparison of Key Differences

Key Terms 

Pseudouridine, Uridine

What is Uridine

Uridine is a pyrimidine nucleoside that contains ribose and uracil bonds together by a β-N1-glycosidic bond. The primary function of uridine is to serve as a nucleoside, making up RNA. However, endogenous synthesis of nucleic acid does not require uridine. In nature, uridine is produced as uridine monophosphate (uridylate) by orotidylate decarboxylation. Orotidylate decarboxylase is the enzyme that catalyzes the reaction. Also, uridine is a non-essential nutrient, and our body produces uridine when needed.

Figure 1: Uridine

Furthermore, dietary sources of uridine include milk products, sugarcane extracts, tomatoes, brewer’s yeast, beer, broccoli, and organ meats. Muscular exercise increases the levels of uridine in the muscles. Apart from that, ethanol ingestion increases the uridine levels in the liver. The uridine leaks into the bloodstream from the liver and muscles, causing an increase in plasma concentration of uridine. In addition, beer increases the plasma concentrations of uridine as it contains a considerable amount of uridine. Therefore, a combination of ingestion of beer and exercise increases the plasma concentration of uridine to a greater degree. Also, uridine plays a vital role in glycogen synthesis. 

What is Pseudouridine

Pseudouridine is a structural isomer of uridine. Here, ribose and uracil are bound together by a carbon-carbon glycosidic bond. The main significant feature of pseudouridine is that RNA undergoes modifications in the presence of pseudouridine. RNA modifications cause discrete changes in a specific nucleotide sequence. It is one of the evolutionarily conserved properties of RNA. However, it can affect the cell’s activity, RNA localization, and RNA stability. RNA modifications can occur in the nucleus, mitochondria, and plastids.

Figure 2: Pseudouridine

Moreover, RNA can be modified in many ways after the synthesis. Therefore, it is a possible way to regulate gene expression post-transcriptionally. In the pseudouridine, the glycosidic bond occurs between the C1 of the ribose sugar and the C5 carbon of the uracil. In contrast, uridine contains C1-N1 glycosidic bond. However, the C-C bond increases rotational freedom and confirmational flexibility. 

Similarities Between Uridine and Pseudouridine

• Uridine and pseudouridine are two isomers.
• They contain ribose sugar and uracil in the structure.
• They occur in cells and cause RNA modifications.

Difference Between Uridine and Pseudouridine

Definition

Uridine is a glycosylated pyrimidine analog containing a β-N1-glycosidic bond between uracil and ribose ring. In contrast, pseudouridine refers to an isomer of the nucleoside uridine in which the uracil is attached via a carbon-carbon instead of a nitrogen-carbon glycosidic bond.

Structure

Uridine contains a nitrogen-carbon glycosidic bond, while pseudouridine contains a carbon-carbon glycosidic bond. 

Function

Urdine is a nucleoside that occurs in the structure of RNA, while pseudouridine causes RNA modifications.

Conclusion

In brief, uridine and pseudouridine are two structural isomers that contain ribose sugar and uracil bound through a glycosidic bond. They occur in cellular RNA. Uridine is a nucleoside that includes a glycosidic bond between nitrogen and carbon. It is the naturally occurring nucleoside form in RNA. In comparison, pseudouridine is an isomeric form of uridine, and its glycosidic bond occurs between carbon and carbon. Also, it is the predominant cause of RNA modifications in cellular RNA. Therefore, the main difference between uridine and pseudouridine is their structure and function. 

References:

1. Uridine. Uridine – an overview | ScienceDirect Topics. (n.d.). 
2. Pseudouridine. Pseudouridine – an overview | ScienceDirect Topics. (n.d.). 

Image Courtesy:

1. “Uridin” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Pseudouridine” By Yikrazuul – Own Work (Public Domain) via Commons Wikimedia