GSTp (Glutathione S-transferase P) is an enzyme that plays an important role in detoxification by catalyzing the conjugation of many hydrophobic and electrophilic compounds with reduced glutathione. GSTP1 is identified as a CDK5 (Cyclin dependent kinase-5) regulatory protein, and is thought to regulates negatively CDK5 activity via p25/p35 translocation. Thus a binding ELISA assay was conducted to detect the interaction of recombinant human GSTp and recombinant human CDK5. Briefly, GSTp were diluted serially in PBS, with 0.01%BSA (pH 7.4). Duplicate samples of 100ul were then transferred to CDK5-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1 h with anti-GSTp pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 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 nm immediately. The binding activity of of GSTp and CDK5 was shown in Figure 1, and this effect was in a dose dependent manner.