Glutathione S Transferase Pi (GSTp) is a key member of the GST enzyme family, widely expressed in mammalian tissues like the liver, kidneys, and lungs. It primarily functions in cellular detoxification, catalyzing the conjugation of glutathione to electrophilic xenobiotics and endogenous reactive species, facilitating their excretion. Beyond detoxification, GSTp also regulates cellular signaling and stress responses—for instance, it modulates oxidative stress by scavenging free radicals and interacts with signaling molecules to influence cell survival. Structurally, it exists as a homodimer, with each subunit containing a glutathione-binding site and a substrate-binding site, enabling its enzymatic and regulatory roles. GSTp specifically binds to Mitogen Activated Protein Kinase 8 (MAPK8), inhibiting MAPK8’s kinase activity to regulate stress and apoptotic pathways.To detect the activity of recombinant GSTp a functional ELISA assay was performed to evaluate the interaction between recombinant pig GSTp and recombinant human MAPK8.Briefly, GSTp was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to MAPK8-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-GSTp pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant pig GSTp and recombinant human MAPK8 was shown in Figure 1, the EC50 for this effect is 0.31µg/mL.