The hydrolysis of phosphotyrosine esters in proteins is catalyzed by a family of enzymes called protein phosphotyrosine phosphatases.

These hydrolyses in many cases involve phosphoenzyme intermediates. The nucleophilic group of the phosphatase (the enzyme) is the thiol group of a cysteine residue in the active site.

Using abbreviated structures like the ones in Eq. 25.22, write a curved-arrow mechanism for the hydrolysis that includes the structure of the phosphoenzyme intermediate. Assume that acids and bases are present in the enzyme active site as needed.

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protein H₂O + H₂C- a phosphorylated tyrosine residue in a protein protein tyrosine phosphatase protein H₂C- OH + HO -P-0 a tyrosine residue in a protein phosphate