Serine/threonine kinases are a type of enzyme that play a crucial role in cellular signaling by adding a phosphate group to the amino acids serine or threonine in proteins. This phosphorylation process can activate or deactivate proteins, influencing various cellular functions such as growth, division, and metabolism. These kinases are involved in numerous biological processes and are essential for regulating pathways like the MAPK pathway and PI3K/Akt pathway. Dysregulation of serine/threonine kinases can lead to various diseases, including cancer, making them important targets for therapeutic interventions.