Protein Tyrosine Phosphatase-1B (PTP-1B) belongs to the family of protein tyrosine phosphatases, which specifically hydrolyze aromatic phosphates and negatively regulate insulin signal transduction by dephosphorylating tyrosine residues on insulin receptors or their substrates.
In the dephosphorylation of PTP-1B, the phosphate group produced reacts with malachite green to form chromogenic substance, PTP-1B in samples is measured by measuring the absorbance change at 636 nm.