Final answer:
CAK is a serine-threonine kinase, which phosphorylates serine or threonine residues in proteins, regulating cell cycle and other cellular processes.
Step-by-step explanation:
The enzyme CAK is a serine-threonine kinase.
This type of enzyme is involved in the process of phosphorylation, where it catalyzes the transfer of a phosphate group from ATP to the hydroxyl groups of serine or threonine residues in target proteins.
Kinases, including serine-threonine kinases like CAK, function as control switches for many cellular functions.
They play crucial roles in signaling cascades and can activate or deactivate other proteins, thus regulating various cellular processes including the cell cycle.
Specifically, CAK is involved in the activation of cyclin-dependent kinases (CDKs) by phosphorylating them.
Cyclins are proteins that regulate the progression of cells through the cell cycle by activating these CDKs.
Two notable examples of serine-threonine kinases are PKA and PKC, which also phosphorylate serine or threonine in target polypeptides, similar to the function of CAK.