Serine/threonine/tyrosine-interacting protein（STYX) is a member of the protein-tyrosine phosphatase family. STYX contains a Gly residue instead of a conserved Cys residue in the dsPTPase catalytic loop which makes it catalytically inactive as a phosphatase. On the other hand， the binding pocket is adequately preserved to bind phosphorylated substrates， and may protect them from phosphatases. STYX may have a role in spermiogenesis. STYX is a possible pseudophosphatase
