Kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. Kinases are part of the larger family of phosphotransferases. Kinases are not to be confused with phosphorylases, which catalyze the addition of inorganic phosphate groups to an acceptor, nor with phosphatases, which remove phosphate groups. The phosphorylation state of a molecule, whether it be a protein, lipid, or carbohydrate, can affect its activity, reactivity, and its ability to bind other molecules. Therefore, kinases are critical in metabolism, cell signalling, protein regulation, cellular transport, secretory processes, and many other cellular pathways.
Protein kinases are a group of enzymes that add a phosphate group to proteins to change their activity. In this process, ATP or GTP is the phosphate group donor, while serine and threonine and tyrosine protein kinases are the receptor. The protein kinase structure is complicated. The function domain of the protein kinase is conservative, which usurally consists of 250 ~ 300 amino acids. Protein kinase can be classified by two ways, one is classified by substrates, including tyrosine kinase, serine threonine kinase and histidine kinase. The other is classified by catalytic domains, including AGC kinase, CAMK kinase, CK1 kinase, CMGC kinase, STE kinase, Tyrosine Kinase and TKL kinase.
Lipid kinases are one of the most promising new classes of potential drug targets. PI-3 and sphingosine kinases regulate a wide variety of cellular functions, including cell growth, proliferation, differentiation, motility, intracellular trafficking, and survival. As a result, defects in lipid kinase function lead to multiple disease states, including several forms of cancer and diabetes.