Inosine monophosphate dehydrogenase, IMPDH, (E.C. 1.1.1.205) is the rate-limiting enzyme in de novo guanine nucleotide biosynthesis and it is essential for lymphocyte proliferation. IMPDH oxidizes inosine 5'-monophosphate (IMP) to xanthine 5'-monophosphate (XMP) using NAD as a cofactor. It plays a critical role in cell growth and in the malignancy of some tumors such as pancreatic, colon and bladder cancers. IMPDH2 is the predominant isoform of IMPDH and is specifically linked to a wide range of cancers and lymphocyte proliferation. IMPDH is recognized as a validated target as antiviral, antiparasitic, antimicrobial, antileukemic and immunosuppressive agents. In BioVison's IMPDH inhibitor screening assay, IMP is oxidized by IMPDH producing a series of intermediates, which react with the probe to generate a colorimetric signal (OD 450 nm). The signal is directly proportional to the IMPDH activity and has a very low background. In the presence of a IMPDH inhibitor such as mycophenolic acid (MPA), the reaction is arrested, thus decreasing the signal. Assay Genie's IMPDH assay is fast, sensitive and reproducible and is suitable for functional assays, high-throughput screening and preclinical studies in drug discovery.

Figure A shows the reaction kinetics in the presence and absence of the IMPDH2 enzyme. B. Inhibition of IMPDH2 enzymatic activity using MPA (IC 50 : 59 nM).