1; class I Cys-based PTPs, class II Cys-based PTPs, class III Cys-based PTPs, and Asp-based PTPs. Each PTP has a characteristic role in a variety of cellular processes including cellular metabolism, growth, proliferation, differentiation and also has been emerged as a therapeutic target in many diseases such as diabetes, leukemia, neurodegradation, and cancer. Class I PTPs comprise dual specificity phosphatases (DUSPs) including VHR that has diverse substrate specificities both or either on phospho-Tyr, phospho-Ser, and phospho-Thr residues. Class II PTPs that dephosphorylate only pTyr are encoded by a single gene ACP1 and related to diseases like Alzheimer’s disease and asthma. Class III PTPs comprise CDC25 family proteins that regulate cell cycle by acting on Cdks. They dephosphorylate Thr-Tyr motifs of N-terminal Cdks, thus keep them from driving the cell progression. 2