This protein functions as a dosage-dependent inducer in mitotic control. It is a tyrosine protein phosphatase required for progression of the cell cycle. It may directly dephosphorylate Cdk1 and activate the Cdk1 activity. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Belongs to the MPI phosphatase family.