Question

The cyclin B–Cdc2 complex controls the passage from G2 into M and is assembled before mitosis however, its catalytic activity is restricted to mitosis. What process is responsible for the activation of the cyclin B–Cdc2 complex?

Answer 1

Phosphorylases that selectively add phosphate groups to the Cdc-2 subunit, thereby activating this complex.

Step-by-step explanation:

The cyclin B-Cdc-2 (also known as maturation-promoting factor or simply MPF) complex is activated when it enters into the nucleus during the G2/M transition in the cell cycle. Cdc-2 is a protein kinase that associates with cyclin proteins. These proteins (cyclins) regulate the cell cycle by activating cyclin-dependent kinases. It is well known that phosphorylation of the Cdc2 subunit at different residues can both activate and inactivate the MPF complex. Moreover, enzymes capable of both inactivating phosphorylases and activating phosphatases have also shown to be able to activate MPF.