Serine/threonine-protein kinase greatwall (Mastl)

Serine/threonine kinase that plays an integral role in M phase by acting as a regulator of mitosis entry and maintenance. Acts by promoting the inactivation of protein phosphatase 2A (PP2A) during M phase: does not directly inhibit PP2A but functions by mediating phosphorylation and subsequent activation of ARPP19 and ENSA in'Ser-62' and'Ser-67', respectively.

ARPP19 and ENSA are phosphatase inhibitors that specifically inhibit the PPP2R2D (PR55-delta) subunit of PP2A. Inactivation of PP2A during M phase is vital to maintain cyclin-B1-CDK1 activity high.