What is the Difference Between Polymerase and Primase

The key difference between polymerase and primase is that polymerase takes part in both replication and transcription while primase takes part only in replication.

Replication of DNA and synthesis of the corresponding mRNA copy play important roles in information flow in organisms. Both are enzyme-mediated functions that involve polymerization activity. Many enzymes and factors are involved in the success of each process.

CONTENTS

1. Overview and Key Difference
2. What is Polymerase
3. What is Primase
4. Similarities – Polymerase and Primase
5. Polymerase vs Primase in Tabular Form
6. Summary – Polymerase vs Primase

What is Polymerase?

Polymerase refers to a group of enzymes that are capable of polymerization, i,e, the synthesis of long chains of nucleic acids. Polymerases can be broadly grouped based on the molecules they polymerize. There are two main polymerases as DNA polymerase and RNA polymerase. The role of DNA polymerase is during the elongation phase of replication, where it adds deoxyribonucleotides to the growing strand. DNA polymerase always adds nucleotides in the 5’ to 3’ direction. DNA polymerase cannot initiate nucleotide addition; hence it requires a short RNA template. Furthermore, it requires clamps to stabilize themselves in the growing chain.

In contrast, RNA polymerase activity starts during transcription elongation. RNA polymerase adds ribonucleotides in the 5’ to 3’ direction. However, RNA polymerases do not require a template and can initiate polymerization independently. Types of polymerases differ among eukaryotes and prokaryotes. However, in all organisms, the polymerase enzyme is a multi-domain enzyme complex.

What is Primase?

DNA primase is an enzyme that plays a key role in DNA replication. It belongs to a type of RNA polymerase where primase catalyzes the synthesis of a short RNA oligonucleotide that acts as a template for DNA polymerase. This short oligonucleotide is called a primer.

Upon binding of the RNA primer, DNA polymerase commences its polymerization. The RNA primer is later removed by exonuclease activity. In bacteria, the primase activity takes place in conjunction with DNA helicase. Thus, it forms a complex helicase to form a primosome. Archeal and eukaryotic primases are heterodimeric proteins with regulatory subunits.

What are the Similarities Between Polymerase and Primase?

• Polymerase and primase are enzymes composed of proteins.
• They possess enzymatic activity.
• Both take part in the process of DNA replication.
• Moreover, both enzymes are present in both eukaryotes and prokaryotes.
• Both enzymes are types of polymerases.

What is the Difference Between Polymerase and Primase?

The key difference between polymerase and primase is based on the process they essentially act on. While polymerase plays an important role in both replication and transcription, primase is essentially needed for the replication process. Apart from this, the type of product they produce, their ability of them to initiate independently, their involvement in PCR varies between the two types of enzymes.

The below infographic presents the differences between polymerase and primase in tabular form for side by side comparison.

Summary – Polymerase vs Primase

Both polymerase and primase are enzymes that belong to the polymerase group of enzymes. However, the key difference between polymerase and primase is based on the process they essentially act on. The polymerase has more diversity and acts on both replication and transcription processes. Primase is mainly confined to the replication process. Both are proteins that show enzymatic function. Moreover, they also differ in the substrates they use for polymerization and their ability to initiate polymerization independently.

Reference:

1. Cooper, Geoffrey M. “DNA Replication.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970.
2. Guilliam, Thomas A, et al. “Primase-Polymerases Are a Functionally Diverse Superfamily of Replication and Repair Enzymes.” Nucleic Acids Research, Oxford University Press, 18 Aug. 2015.

Image Courtesy:

1. “0323 DNA Replication” By OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Primase” By Fdardel – Own work (CC BY-SA 3.0) via Commons Wikimedia