PTPN2 and obesity due to melanocortin 4 receptor deficiency: PTPs were extensively oxidized in HFD mice livers, compared with those in chow-fed mice livers, and the PTP oxidation was irreversible due to the -SO3H. These oxidized PTPs included PTP1B and TCPTP, which suggests the consequential redox regulation of TCPTP in obesity-induced oxidative stress [109].