What are protein kinases?
A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them by a process known as phosphorylation. This usually results in change in the activity of the protein to which the phosphate group is added, like change in enzyme activity, cellular location, or association with other proteins. Up to 30% of all proteins may be modified by kinase activity, and kinases are impotant class of cellular enzymes which regulate the behavior of the cells like, signal transduction, the transmission of signals within the cell. The human genome contains about 500 protein kinase genes; they constitute about 2% of all eukaryotic genes.
How do protein kinases act?
Protein kinases act by adding or removing a phosphate group from the energy source of the cell known as “ATP” and attaching it to the proteins. Proteins are made of amino acids and there are several of them. Depending on the amino acid group in the protein to which the kinases attach the phosphate group, they are called serine threonine kinases (when they act on amino acid serine and threonine) or tyrosine kinases (when they act on the amino acid tyrosine). Some kinases act on all of the three amino acids and are said to have dual specificity.
What is the role of Kinases in cellular activity?
Protein kinases have profound effects on a cell. They act on a variety of substrates in the cell including
- Proteins which constitute the cell membrane – known as structural proteins.
- Metabolic enzymes which digest the various metabolic products in the cell.
- Proteins which control the division of the cell known as cell cycle
- And transcription factors- which start the process of activation of gene.
The main function of the protein kinases is transmission of the signal within the cell known as signal transduction. Pathways involved in signal transduction is important in all cellular processes like
Obviously, the activity state of these proteins determines the fate
of the cell; aberrant expression and activities of these functional classes
of enzymes result in abnormal signal transmission. Deregulated kinase
activity is a frequent cause of disease, particularly cancer, because
kinases regulate many aspects that control cell growth, movement and death.
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