Question

Is a cytoplasmic calcium ion influx sufficient to inactivate MAP kinase?

Answer 1

Yes, the cytoplasmic calcium ion influx is sufficient to inactivate MAP kinase.

Normally the MAPK inactivation happens during fertilization because the high level of MAPK has been reported to inhibit the fertilized egg of starfish, sea urchin, and mammals from entering into M phase of cell cycle.

Ca2+ ions are responsible for inactivation of MAPK by

1. activation of a Thr/ Tyr phosphorylase enzyme that inactivates the MAPKK
2. thus if MAPKK is inactivated, MAPK will be automatically inactivated

It has been reported that when cells having cytoplasmic calcium ions are subjected to an external zero calcium ion environment, MAPK activity was still absent from the cell

This shows that the cytoplasmic concentration of calcium ions is sufficient for MAPK inactivation.