Cylin dependent kinases

Cyclin Dependent Kinases (Cdk) are enzymes associated with different checkpoints within the eukaryotic cell cycle. They belong to the family of enzymes; kinases, and work by phosphorylating proteins thus, activating or deactivating other protiens or pathways within the cell. Cyclin dependent kinases as the name suggests are dependent on a protein called cyclin, which at differing periods within the cell cycle is readily available to bind to Cdk's. This high affinity binding of the Cdk and the cyclin protein activates the enzyme activity within the kinase. The Cdk's occur at checkpoints within the cell cycle as I mentioned earlier, these checkpoints occur at the end of the G₁ phase throughout the S phase and on entry to the M phase . These checkpoints act as a window of choice within the cell cycle where by the cell can either continue on to the next stage, enter a stage of quiesence called G₀ or induce the nessecary mechanisms for programmed cell death, or apoptosis.