Protein tyrosine phosphatase molecule. Computer model of the secondary structure of an intermediate form of protein tyrosine phosphatase. Beta-sheets are purple and alpha-helices are blue. This transient cysteinyl-phosphate intermediate molecule is formed when the enzyme removes a phosphate group from (dephosphorylates) a tyrosine residue on a protein. The phosphorylation status of a protein moderates its function and is under the control of hormones and genes.