IMPDH2 belongs to the IMPDH/GMPR family. It catalyzes the NAD-dependent oxidation of inosine-5'-monophosphate into xanthine-5'-monophosphate, which is then converted into guanosine-5'-monophosphate. IMPDH2 is the rate-limiting enzyme in the de novo guanine nucleotide biosynthesis. It is thus involved in maintaining cellular guanine deoxy- and ribonucleotide pools needed for DNA and RNA synthesis. Also IMPDH1 and IMPDH2 are targets for the important immunosuppressive drug, mycophenolic acid (MPA). Recombinant human IMPDH2 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.