Difference Between Kinase and Phosphorylase

Key Difference – Kinase vs Phosphorylase
 

Both Kinase and Phosphorylase are enzymes that deal with phosphate though there lies a difference in their function and nature. The key difference between them is that, Kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP molecule to a specified molecule whereas phosphorylase is an enzyme that introduces a phosphate group into an organic molecule, particularly glucose. This article will introduce you to kinase and phosphorylase enzymes that deal with phosphate and explain what are the differences between kinase and phosphorylase.

What is Phosphorylase?

Phosphorylases were discovered by Earl W. Sutherland Jr. in the late 1930s. These enzymes catalyze the addition of a phosphate group from an inorganic phosphate or phosphate+hydrogen to an organic molecule acceptor. As an example, glycogen phosphorylase can catalyze the synthesis of glucose-1-phosphate from a glucan including a glycogen, starch or maltodextrin molecule. The reaction is known as a phosphorolysis which is also similar to a hydrolysis.  However, the only dissimilarity is that it is a phosphate, not a water molecule that is placed on the bond.

What is Kinase?

Kinase enzyme can catalyze the transfer of phosphate groups from high-energy, phosphate-donating molecules to particular substrates. This process is identified as phosphorylation when the substrate gains a phosphate group and the high-energy molecule of ATP donates a phosphate group. In this phosphorylation process, kinases play a significant role, and it is a part of the larger family of phosphotransferases. Thus, kinases are very important in cell metabolism, protein regulation, cellular transport, and numerous cellular pathways.

What are the differences between Kinase and Phosphorylase?

Definition of Kinase and Phosphorylase

Kinase: Kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to particular substrates.

Phosphorylase: Phosphorylase is an enzyme that catalyzes the addition of a phosphate group from an inorganic phosphate or phosphate+hydrogen to an organic molecule acceptor.

Characteristics of Kinase and Phosphorylase

Mechanism of action

Kinase: Catalyze the transmission of a terminal phosphate group of ATP to an -OH group on a substrate. Thereby produce a phosphate ester bond in the product. The reaction is known as phosphorylation, and the overall reaction is written as,

Phosphorylase: Catalyze the introduction of a phosphate group into an organic molecule. The reaction is known as a phosphorylysis and the overall reaction is written as,

Phosphate donor in the reaction of kinase and phosphorylase enzymes

Kinase: Phosphate group from ATP molecule

Phosphorylase: Phosphate group from inorganic phosphate

Substrate of kinase and phosphorylase enzymes

Kinase: Specific organic molecules such as carbohydrate, protein or lipid

Phosphorylase: Organic molecule mainly glucose

End products of kinase and phosphorylase enzymes

Kinase: ADP (energy molecule) + phosphorylated substrate

Phosphorylase: If the substrate is glucose it can produce glucose-1-phosphate

Structure of kinase and phosphorylase enzymes

Kinase: Kinase is a very complex tertiary structure protein.

Phosphorylase: Biologically active form of phosphorylase is a dimer of two equal protein sub units. For example, glycogen phosphorylase is a huge protein, contained with 842 amino acids and mass of 97.434 kDa. The glycogen phosphorylase dimer has several sections of biological importance, including catalytic sites, glycogen binding sites as well as allosteric sites.

Regulation of kinase and phosphorylase enzyme

Kinase: Kinases activity is highly regulated, and they have intense effects on a cell. Kinases are activated on or off by phosphorylation, by binding of protein activator or protein inhibitor or by governing their location in the cell in relation to their substrates.

Phosphorylase: Glycogen phosphorylase is regulated by both allosteric control and by phosphorylation. Hormones such as epinephrine and insulin can also regulate glycogen phosphorylase.

Classification of kinase and phosphorylase enzymes

Kinase: Kinases are categorized into comprehensive groups by the substrate they act upon such as protein kinases, lipid kinases, and carbohydrate kinases.

Phosphorylase: The phosphorylases categorized into two; Glycosyltransferases and Nucleotidyltransferases. Examples for Glycosyltransferases are,

• glycogen phosphorylase
• starch phosphorylase
• maltodextrin phosphorylase
• Purine nucleoside phosphorylase

Example for Nucleotidyltransferases is,

• Polynucleotide Phosphorylase

Pathology of kinase and phosphorylase enzymes

Kinase: Decontrolled kinase activity can cause cancer and disease in humans, including certain types of leukemia and many others because kinases regulate many phases that control cell cycle including growth, movement, and death.

Phosphorylase: Some mediacal conditions like glycogen storage disease type V – muscle glycogen and glycogen storage disease type VI – liver glycogen, etc. are  associated with phosphorylases.

 

References

Chang. S., Rosenberg, M.J., Morton, H., Francomano, C.A. and Biesecker, L.G. (1998). Identification of a mutation in liver glycogen phosphorylase in glycogen storage disease type VI. Hum. Mol. Genet., 7(5): 865–70.

Ciesla, J., Frączyk, T. and Rode, W. (2011). Phosphorylation of basic amino acid residues in proteins: important but easily missed. Acta Biochimica Polonica, 58(2): 137–147.

Hunter, T. (1991). Protein kinase classification. Methods in Enzymology, 200: 3–37.

Johnson, L. N. (2009). The regulation of protein phosphorylation. Biochem Soc. Trans., 37(2): 627–641.

Johnson, L. N. and Barford, D. (1993). The effects of phosphorylation on the structure and function of proteins. Annual review of biophysics and biomolecular structure, 22(1): 199-232.

Manning, G. and Whyte, D. B. (2002). The protein kinase complement of the human genome. Science, 298(5600): 1912–1934.

 

Image Courtesy:

“Active site of Dihydroxyacetone Kinase” by Bdoc13 – Own work.  (CC BY-SA 3.0) via Wikimedia Commons

 “Crystal structure 1E3P”. ( Public Domain) via Wikimedia Commons