Isopentenyl-diphosphate isomerase 1, also known as IDI1, is a member of the IPP isomerase type I family and is involved in cholesterol biosynthesis. IDI1 is a peroxisomally-localized enzyme that catalyzes the interconversion of isopentenyl diphosphate (IPP) to its highly electrophilic isomer, dimethylallyl diphosphate (DMAPP), which is the substrates for the successive reaction that results in the synthesis of farnesyl diphosphate and, ultimately, cholesterol. Recombinant human IDI1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.