which is a function of cyclins
Cyclins go hand in hand with kinases. Cyclins do not cause a cell to progress in the cell cycle because cyclins are mere proteins that regulate the rate of the process, and how fast the cell progresses through this process. Cyclins also act by binding to various kinases, which are enzymes that transfer a phosphate group from ATP to other enzymes. The phosphate group activates these enzymes. The quantity of these kinases in the cell remains steady throughout the cell cycle; however they are active only when bound to cyclins.