AAT Bioquest

What are the differences between cyclins and cyclin dependent kinases?

Posted June 9, 2023


Basis of differentiation


Cyclin dependent kinases


Cyclins are regulatory molecular proteins involved in the cell cycle that have no enzymatic function on their own

Cyclin dependent kinases are catalytic proteins involved in the cell cycle that possess enzymatic function after activation by cyclins

Molecular weight

45 kDA to 87 kDa

34 kDa to 40 kDa


Expressed at specific stages of the cell cycle in

Expressed continuously throughout the cell cycle 


Cyclins bind to CDKs in order to activate them and create maturation promoting factors that phosphorylate target proteins 

CDKs are the catalytic molecules responsible for phosphorylating target proteins which drive cell cycle progression. They phosphorylate wide ranges of substrates to facilitate events of the cell cycle  

Additional resources

Cyclins and cyclin-dependent kinases: a biochemical view.

Cell Meter™ Fluorimetric Live Cell Cycle Assay Kit *Optimized for 405 nm Violet Laser Excitation*

Cell Cycle Assays