PTPN1 and obesity due to melanocortin 4 receptor deficiency: Protein-tyrosine phosphatase 1B (PTP-1B), also called protein tyrosine phosphatase non-receptor type 1, is a member of the protein tyrosine phosphatases (PTPs; EC 3.1.3.48) family that plays a role in controlling T2D and obesity [16,29].