Kinases, its function and different types

#biotechnology #cellsignaling #kinases #phosphorylation
Protein kinases (PTKs) are enzymes that regulate the biological activity of proteins by phosphorylation of specific amino acids with ATP as the source of phosphate, thereby inducing a conformational change from an inactive to an active form of the protein or vice versa.
The human genome contains about 500 protein kinase genes and they constitute about 2% of all human genes. Protein kinases are also found in bacteria and plants. Up to 30% of all human proteins may be modified by kinase activity, and kinases are known to regulate the majority of cellular pathways, especially those involved in signal transduction.
Types of kinases
1. Serine/threonine kinases
2. Tyrosine Kinases
3. Dual specificity kinases
4. Histidine kinases
Serine/threonine kinases
A serine/threonine-protein kinase is a kinase enzyme that phosphorylates the OH group of serine or threonine (which have similar sidechains). At least 125 of the 500+ human protein kinases are serine/threonine kinases (STK).
The chemical reaction performed by these enzymes can be written as
ATP + a protein ----------- ADP + a phosphoprotein
Thus, the two substrates of this enzyme are ATP and a protein, whereas its two products are ADP and phosphoprotein.
Raf (Rapidly accelerated fibrosarcoma) or (MAPKKK)
Tyrosine kinases
A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine amino acid of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Examples are SRC, ABL, FAK and Janus kinase
Dual specificity kinases
A dual-specificity kinase is a kinase that can act as both tyrosine and serine/threonine kinase. MEKs, involved in MAP kinase pathway, is an example of dual-specificity kinases.
Histidine kinase
A histidine kinase is an enzyme that can transfer a phosphate group from ATP to the histidine amino acid of specific proteins inside a cell.

MAPK signaling pathway:    • Fibroblast Growth factor (FGF) and si...