Purification and characterization of the low molecular weight protein tyrosine phosphatase, Stp1, from the fission yeast Schizosaccharomyces pombe

The low molecular weight protein tyrosine phosphatase (low Mr PTPase), Stp1, produced by the yeast Schizosaccharomyces pombe, acts as a phosphatase to aryl and alkyl phosphates and dephosphorylatess phosphotyrosyl peptides and proteins. The amino acid sequence of Stp1 is similar to that of mammalian low Mr PTPase but its activity is almost six times slower. The decomposition of the enzyme intermediate is the rate limiting step in the reaction. Low Mr PTPase are probably dual specificity enzymes as bovine low Mr PTPase removes the phosphate from phosphotyrosyl and phosphoseryl/threonyl proteins.