Function and regulation of cdc25 protein phosphate through mitosis and meiosis.

Activation of the cyclin B-cdc2 kinase mitotic inducer involves dephosphorylation of two inhibitory residues, tyrosine 15 and threonine 14, cdc25 is the specific phosphatase that directly dephosphorylates and activates the cdc2 kinase, cdc25 activity is regulated by phosphorylation. Both phosphatases 1 and 2A could act as cdc25-specific inhibitory phosphatases. Although the cyclin B-cdc2 complex plays a role in activating cdc25, it is highly probable that a distinct protein kinase is involved as a trigger in cdc25 activation. The implication of raf kinase as a cdc25-specific activating kinase in human cells and Xenopus oocytes is discussed.