Claim: PTPN1 isolated from a human placental protein extract, and is also in the cytoplasmic face; it can also be found in mice and cause insulin sensitivity.
Evidence: PTP1B was first isolated from a human placental protein extract, but it is expressed in many tissues. PTP1B is localized to the cytoplasmic face of the endoplasmic reticulum. In mice, genetic ablation of PTPN1 results in enhanced insulin sensitivity.