CDK2, short for Cyclin-Dependent Kinase 2, is a serine/threonine-specific protein kinase that plays a crucial role in the regulation of the cell cycle. It belongs to the cyclin-dependent kinase (CDK) family of enzymes, which are essential for controlling the progression of cells through the various stages of cell division. CDK2 functions in complex with regulatory proteins called cyclins, particularly cyclin E during the G1/S transition and cyclin A during S phase and G2 phase. This cyclin-CDK2 complex is responsible for phosphorylating numerous substrates, including other kinases and transcription factors, that are critical for driving the cell cycle forward. The activity of CDK2 is tightly regulated by a variety of mechanisms, including phosphorylation, dephosphorylation, and interaction with inhibitory proteins like p21 and p27. Dysregulation of CDK2 activity has been implicated in the development of numerous diseases, including cancer. In cancer cells, CDK2 is often overexpressed or mutated, leading to uncontrolled cell proliferation and tumor growth. As such, CDK2 has become a target for the development of anticancer therapies aimed at inhibiting its activity and blocking the progression of cancer cells through the cell cycle.