Kinases transfer phosphate groups to substrates, activating cellular processes. Kinase phosphorylation involves protein kinases and coenzymes like ATP. Specific amino acids act as substrates, with serine being the most common. Dysfunctions in kinase phosphorylation can lead to uncontrolled cell growth and cancer. Tyrosine kinase inhibitors can block these malfunctions.
Kinases are catalysing enzymes that transfer phosphate groups from a high-energy molecule to a substrate. This transfer of phosphate groups is called kinase phosphorylation. Important cellular processes are turned on and off by kinase phosphorylation. Failure of this system can lead to abnormal cell behavior, which can cause cancer cells to grow.
Enzymes act as catalysts to speed up the rate of chemical reactions. Kinase phosphorylation involves protein kinases that exist on and within the cell membrane. Phosphorylation occurs intracellularly.
A phosphate group is removed during the phosphorylation of the kinase. Phosphate groups contain a central phosphate atom surrounded by four oxygen atoms. The group is taken from a coenzyme such as adenosine triphosphate (ATP). This coenzyme has three phosphate groups and binds well with proteins.
The kinase phosphorylation process directs the phosphate group to specific amino acid substrates. Located on the outside of the cell membrane, these amino acids have open hydroxyl groups which allow the phosphate group to attach. Serine, threonine and tyrosine are potential substrates for protein kinase.
There are kinases that can only attach to a specific substrate and others that can attach to all three simultaneously. Serine is the most commonly used substrate. Specific kinases are named after their corresponding substrates, such as tyrosine kinase, which plugs into the tyrosine substrate.
The extracellular kinase binding sites around the amino acids also include growth factor proteins. The initiation and regulation of cell cycles involves growth factors. The kinase and growth factors flip cellular actions much like an on and off switch.
The addition of the phosphate group during kinase phosphorylation changes the shape and actions of the protein. This turns on, or activates, the cellular action. At the end of the action, the added phosphate group is removed to deactivate the action. A mutated kinase can disrupt this process and cause cellular actions to become unregulated.
A dysfunction of the receptor tyrosine kinases during the kinase phosphorylation process can lead to uncontrolled cell growth and division. This has the potential to cause the growth of oncogenes that turn normal cells into cancer cells. There is a class of anticancer drugs called tyrosine kinase inhibitors that work to block malfunctions in the tyrosine kinase causing oncogenes.
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