What is the Difference Between RNASE A and RNASE H

The main difference between RNase A and RNase H is that the RNase A is specific for single-stranded RNAs, whereas RNase H is specific for RNA in a DNA: RNA duplex. Furthermore, RNase A produces 2′,3′-cyclic monophosphate intermediates while RNase H produces single-stranded RNA. Moreover, RNase A is more common in research while the main function of RNase H is to remove RNA primers from Okazaki fragments.  

RNase A and RNase H are two major types of endoribonucleases which cleave RNA molecules. 

Key Areas Covered 

1. What is RNase A
     – Definition, Features, Importance
2. What is RNase H
     – Definition, Features, Importance
3. What are the Similarities Between RNase A and RNase H
     – Outline of Common Features
4. What is the Difference Between RNase A and RNase H
      – Comparison of Key Differences

Key Terms 

Cofactors, Endoribonucleases, RNA, RNase A, RNase H

What is RNase A 

RNase A is a type of endoribonuclease used in research. Bovine pancreatic ribonuclease A is an example of RNase A in the lab. Generally, it is a type of hardiest enzyme isolated by boiling a crude extract under denatured conditions. Furthermore, RNase A is specific for single-stranded RNA molecules.

Figure 1: RNase A

Therefore, RNase A cleaves unpaired C and U residues, forming a 3′ phosphorylated product through a 2′,3′-cyclic monophosphate intermediate. However, it does not require a cofactor for its enzymatic activity. 

What is RNase H  

RNase H is another endoribonuclease whose main function is to cleave RNA primers in Okazaki fragments. Therefore, the specificity of the enzyme is to RNA in the DNA: RNA duplexes. Ultimately, it produces 5′ phosphorylated single-stranded RNA molecules.

Figure 2: Proposed Mechanism of RNase H

Moreover, RNase H is a non-specific enzyme. Although it uses a hydrolytic mechanism to cleave RNA same as in RNase A, RNase H uses divalent metal ions bound to the enzyme as cofactors. 

Similarities Between RNase A and RNase H  

• RNase A and RNase H are two types of endoribonucleases. 
• They degrade RNA molecules in different stages. 
• Moreover, their mechanism of action is to cleave phosphodiester bonds between RNA nucleotides.  
• They are important in research. 

Difference Between RNase A and RNase H 

Definition 

RNase A refers to an enzyme which promotes the breakdown of RNA into oligonucleotides and smaller molecules while RNase H refers to an endoribonuclease which specifically hydrolyzes the phosphodiester bonds of RNA, which is hybridized to DNA. 

Specificity 

Moreover, RNase A is specific for single-stranded RNAs, whereas RNase H is specific for RNA in a DNA: RNA duplex.  Thus, this is an important difference between RNase A and RNase H.

Products 

Also, while RNase A produces 2′,3′-cyclic monophosphate intermediates, RNase H produces single-stranded RNA. 

Product Phosphorylation 

Another difference between RNase A and RNase H is that RNase A forms 3′ phosphorylated products while RNase H forms 5′ phosphorylated products. 

Cofactors 

Furthermore, RNase A does not require any cofactors while RNase H uses divalent metal ions as cofactors. 

Importance 

Moreover, RNase A is more common in research while the main function of RNase H is to remove RNA primers from Okazaki fragments. 

Conclusion 

In brief, RNase A is an endoribonuclease enzyme mostly used in research. Generally, it is specific for single-stranded RNA molecules. It forms a 3′ phosphorylated product through 2′,3′-cyclic monophosphate intermediates. On the other hand, RNase H is another endoribonuclease enzyme specific for RNA in DNA: RNA duplex. Furthermore, it produces 5′ phosphorylated single-stranded RNA. Therefore, the main difference between RNase A and RNase H is their mechanism of action.   

References:

1. Maruzani, Rugare. “DNA Retroviral Reverse Transcriptase, RNAse H and RNAse A.” Rgmznx, Blog | Rugare M, 19 Feb. 2017, Available Here.
2. “RNase H.” RNase H – an Overview | ScienceDirect Topics, Available Here.

Image Courtesy:

1. “RNase A” By No machine-readable author provided. Vossman assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims). (CC BY-SA 2.5) via Commons Wikimedia   
2. “HIV-1 RNase H Mechanism” By Aeschines – Own work (CC0) via Commons Wikimedia