Phosphorylation is the most important process for plants as well as animals i.e. for the whole world. This is the process in which plants convert the ADP (adenosine diphosphate) to ATP (adenosine triphosphate). We all know that ATP is known as biological coins. ATP needs in every Bio-chemical process in plants such as the photosynthesis process. This photosynthesis process is the most important process for not only the plants but also for both animals as well as the plants because by using this particular process plants make food for them. On the contrary, man that means all the animals on the earth dependable on plants for food. Besides, plants produce oxygen as a byproduct of photosynthesis and animals are totally dependent on oxygen for their breathing. ATP is an important element for photosynthesis.
At the same, dephosphorylation is the reverse process of phosphorylation i.e. plants break down the ATP to produce ADP and Pi with some energy which is spent in many biochemical processes.
Enzymes in the Phosphorylation and Dephosphorylation
The phosphorylation and dephosphorylation process is controlled by the Enzymes. Enzymes play a great role in the phosphorylation and dephosphorylation process.
How do the enzymes control the phosphorylation and dephosphorylation process? Let’s discuss the facts-
- Phosphorylation reactions are catalyzed by a family of enzymes called protein kinases that use adenosine triphosphate (ATP) as a phosphate donor in the biochemical process and break down the ATP and produce ADP and Pi.
- Phosphate groups are cleaved from phosphorylated enzymes by the action of phosphoprotein phosphatases.
- Amino acids with –OH groups are targets for the phosphorylation process.
A significant instance of phosphorylation regulation is seen in muscle and liver. The glycogen phosphorylase is one of the enzymes that catalyze phosphorylation. This enzyme catalyzes the following biochemical reaction to produce glucose and glucose-1-phosphate from glycogen.
Glycogen phosphorylase acts in two forms. They are-
- the more active phosphorylase a and
- the less active phosphorylase b.
Phosphorylase a is the more active form of glycogen phosphorylase which is associates with phosphate inorganic (Pi) and is derived from the less active form of glycogen phosphorylase. On the other side, phosphorylase b is the less active form of glycogen phosphorylase which does not contain a phosphate group but hydroxyl groups. It is also derived from the more active form of glycogen phosphorylase by the act of an enzyme.
How can enzyme activity be controlled by phosphorylation?
- Phosphorylation relates to a phosphate being added to one of a protein’s (enzyme’s) amino acid side chains.
- Phosphates are charged negatively (each phosphate group carrying two negative charges). Therefore the phosphate alters the protein’s features by adding two negative charges to a protein.
- This process is often a conformational change, which causes the protein to shift its structure.
So the Enzyme’s activities can be controlled by the phosphorylation process. For example, Enzymatic conformational changes in phosphorylation are dramatically apparent in the structure of Insulin Receptor Kinase (IRK) determined in the phosphorylated and non-phosphorylated states.