Kinase

A kinase is a type of enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules, typically adenosine triphosphate (ATP), to specific target molecules (substrates). This process is known as phosphorylation, and it is a crucial mechanism for regulating a vast array of cellular processes.

Phosphorylation by kinases can alter the structural conformation, activity, interactions with other proteins, and cellular location of the substrate protein. Consequently, kinases play a fundamental role in signal transduction, cell cycle regulation, metabolism, gene expression, apoptosis, and cellular differentiation.

Kinases are classified as transferases and are highly specific for both the phosphate donor (usually ATP) and the substrate. The active site of a kinase contains regions that bind ATP and the target protein, facilitating the transfer of the terminal phosphate group from ATP to a specific amino acid residue on the substrate. The most commonly phosphorylated amino acids are serine, threonine, and tyrosine, leading to the classification of kinases as serine/threonine kinases or tyrosine kinases, respectively. Dual-specificity kinases can phosphorylate all three of these amino acids.

The human genome encodes hundreds of different kinases, representing about 2% of all human genes. This large number reflects the critical importance of kinases in cellular regulation and their involvement in numerous signaling pathways. Due to their significance, kinases are frequent targets for drug development, particularly in the context of cancer and other diseases where kinase activity is dysregulated.

Kinase activity is itself tightly regulated by a variety of mechanisms, including phosphorylation, binding of regulatory proteins, and changes in cellular localization. Dysregulation of kinase activity can lead to a wide range of diseases, including cancer, diabetes, and inflammatory disorders.