What is the Difference Between Cyclins and Cyclin Dependent Kinases?

Cyclins and cyclin-dependent kinases (CDKs) are both involved in the regulation of the cell cycle, but they have distinct roles and characteristics. Here are the main differences between them:

1. Function: Cyclins are a family of proteins that have no enzymatic activity of their own but activate CDKs by binding to them. CDKs are a family of multifunctional enzymes that can modify various protein substrates involved in the cell cycle.
2. Activity: Cyclins activate CDKs, making them functional enzymes that can phosphorylate (attach phosphate groups to) specific target proteins. The attached phosphate group acts like a switch, making the target protein more or less active.
3. Cell cycle stages: Cyclins are named according to the stage at which they act during the cell cycle, such as G1-phase cyclins, G1/S-phase cyclins, S-phase cyclins, and M-phase cyclins. CDKs, on the other hand, exist in similar amounts throughout the entire cell cycle.
4. Presence and abundance: All eukaryotes have multiple cyclins, each of which acts during a specific stage of the cell cycle. Different types of eukaryotic cells contain different types and numbers of CDKs.

In summary, cyclins are proteins that activate CDKs, which are enzymes that modify target proteins involved in the cell cycle. Cyclins are named according to the stage of the cell cycle they act in, while CDKs are present throughout the entire cell cycle.

Comparative Table: Cyclins vs Cyclin Dependent Kinases

Cyclins and cyclin-dependent kinases (CDKs) are both involved in the regulation of the cell cycle, but they have distinct functions and characteristics. Here is a table summarizing their differences:

Cyclins are regulatory proteins that have no enzymatic function and are involved in the cell cycle. They are expressed at specific stages of the cell cycle in response to various molecular signals and are responsible for determining the activity of CDKs. There are four classes of cyclins: G1 cyclins, G1/S cyclins, S-phase cyclins, and M-phase cyclins.

On the other hand, cyclin-dependent kinases (CDKs) are catalytic proteins involved in the cell cycle that have an enzymatic function. They are serine/threonine kinases whose catalytic activities are regulated by interactions with cyclins. CDKs are divided into three major classes: G1, S, and M-phase CDKs. They play important roles in cell cycle regulation by phosphorylating target proteins.