Has phosphatase activity with the synthetic substrate 6,8-difluoro-4-methylumbelliferyl phosphate (in vitro). Has almost no detectable activity with phosphotyrosine, even less activity with phosphothreonine and displays complete lack of activity with phosphoserine. The poor activity with phosphotyrosine may be due to steric hindrance by bulky amino acid sidechains that obstruct access to the active site. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Monomer. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily.