Main Difference – Kinase vs Phosphorylase
Kinase and phosphorylase are two types of enzymes that are involved in the transformation of phosphate groups into substrates. Both kinase and phosphorylase are essential for the regulation of cellular functions. Kinase transfers a phosphate group from an ATP to a particular substance whereas phosphorylase adds phosphate groups to organic molecules such as glucose. Kinases use phosphate groups from high energy molecules such as ATP. But, phosphorylases use phosphate groups from inorganic phosphates. The main difference between kinase and phosphorylase is that kinase is not involved in breaking bonds in the substrate during the addition of phosphate groups whereas phosphorylase breaks the bond between the substrate and the monomer by adding a phosphate group.
Key Areas Covered
1. What is a Kinase
– Definition, Mechanism of Action, Role
2. What is a Phosphorylase
– Definition, Mechanism of Action, Role
3. What are the Similarities Between Kinase and Phosphorylase
– Outline of Common Features
4. What is the Difference Between Kinase and Phosphorylase
– Comparison of Key Differences
Key terms: Adenosine Triphosphate (ATP), Cell Signaling, Dephosphorylation, Glucans, Kinase, Phosphorylase, Phosphorylation, Substrate
What is a Kinase
Kinase refers to the enzyme that catalyzes the transfer of a phosphate group from an ATP molecule to a particular substance. Kinases are involved in the phosphorylation of proteins, lipids, simple carbohydrates and nucleic acids. In proteins, kinase adds phosphate groups to the amino acids such as tyrosine, threonine, and serine. The phosphorylation and dephosphorylation of proteins are important in cell signaling since the phosphorylated and the dephosphorylated stages of proteins exhibit different activities inside the cell. The action of the kinase enzyme is shown in figure 1.
Figure 1: Action of Kinase
The phosphorylation of lipid molecules is important in maintaining the molecular composition of the plasma membrane. The phosphorylated forms of inositol molecules serve as second messengers as well. The phosphorylation of nucleosides forms nucleotides, which are the building blocks of both DNA and RNA. Carbohydrate kinases add phosphate groups to simple organic molecules such as glucose and fructose.
What is a Phosphorylase
Phosphorylase refers to any enzyme that catalyzes phosphorylation by means of inorganic phosphates. Phosphorylases are mainly involved in the hydrolysis of polysaccharides (glucans) such as glycogen and starch. The most common type of phosphorylase is the glycogen phosphorylase, which transfers phosphate group into a glucose monomer in the glycogen molecule to produce glucose 6-phosphate molecule. This shows that the action of the phosphorylase enzyme is involved in the breakdown of bonds in the polymeric molecules. The action of glycogen phosphorylase is shown in figure 2.
Figure 2: Glycogen Phosphorylase
Glycosyltransferases and nucleotidyltransferases are the two classes of phosphorylases. Glycosyltransferases are enzymes that remove glucose residues from glucans. Nucleotidyltransferases are enzymes with 3’ to 5’ exonuclease activity.
Similarities Between Kinase and Phosphorylase
- Both kinase and phosphorylase are two types of enzymes that are involved in the transformation of phosphate groups between molecules.
- Both kinase and phosphorylase add phosphate groups to organic molecules.
- Both kinase and phosphorylase are important in the regulation of the cellular processes.
- Both kinases and phosphorylases can be regulated by phosphorylation.
Difference Between Kinase and Phosphorylase
Definition
Kinase: Kinase refers to an enzyme that catalyzes the transfer of a phosphate group from an ATP molecule to a particular substance.
Phosphorylase: Phosphorylase refers to an enzyme which catalyzes phosphorylation by means of inorganic phosphates.
Mechanism of Action
Kinase: Kinase transfers a phosphate group from an ATP to a particular substance.
Phosphorylase: Phosphorylase adds phosphate groups to organic molecules such as glucose.
Phosphate Group
Kinase: Kinase uses a phosphate group from ATP.
Phosphorylase: Phosphorylase uses inorganic phosphate groups.
Substrate
Kinase: Kinase adds phosphate groups to organic substrates such as proteins, lipids, simple carbohydrates and nucleic acids.
Phosphorylase: Phosphorylase adds phosphate groups to monomeric units of the glucan such as starch and glycogen.
Bond Breaking
Kinase: Kinases add phosphate groups to existing organic molecules. They do not break the bonds in the substrate.
Phosphorylase: The addition of phosphate groups by phosphorylases break bonds in the substrate.
Regulation
Kinases: Kinases are regulated by phosphorylation.
Phosphorylase: Phosphorylases are regulated by either phosphorylation or allosteric regulation.
Examples
Kinase: Protein kinases, lipid kinases, and carbohydrate kinases are examples of kinases.
Phosphorylase: Glycogen phosphorylase, starch phosphorylase, and polynucleotide phosphorylase are examples of phosphorylases.
Conclusion
Kinase and phosphorylase are two types of enzymes that add phosphate groups to substrates. Kinases use phosphate groups from high energy molecules such as ATP while phosphorylases use phosphate groups from inorganic phosphates. The addition of phosphate groups to the substrate by kinases does not promote the breakdown of bonds in the substrate. But the addition of phosphate groups break down the bonds in the substrate or hydrolyzes the substrate, generating monomer units. Therefore, the main difference between kinase and phosphorylase is the mechanism of action of each type of enzyme during the addition of phosphate groups.
Reference:
1. Cooper, John A. “Kinase.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 19 Jan. 2009, Available here.
2.“Phosphorylase.” Wikipedia, Wikimedia Foundation, 4 Oct. 2017, Available here.
Image Courtesy:
1.”Basic phosphorylation reaction” By Bdoc13 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Glycogen phosphorylase2” By Jmun7616 – Own work (Public Domain) via Commons Wikimedia
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