The right answer is Regulating protein agents.
The regulating protein agents they are talking about is certainly the cyclin, especially cyclin B.
Cyclins have no enzymatic activity, they are regulatory proteins necessary for Cdk to be enzymatically active.
The activation of the Cyclin B / Cdk1 stock is the result of a series of complex and interdependent reactions:
When replication is complete, the Cdc25 phosphatase is no longer sequestered in the cytoplasm and passes into the nucleus, and at the end of the G2 phase, the Cdc phosphatase is activated, probably by phosphorylation by the Polo kinase. Cdc 25 then acts to remove the two phosphates inhibitors Cyclin B / Cdk 1 (after that, there is a process of self-activation).
Cyclin B / Cdk 1 complexes, once activated, allow entry into mitosis. For this, they intervene by triggering a number of phenomena that take place at the beginning of mitosis, that is to say in prophase.
