Isopentenyl-diphosphate isomerase 1（IDI1) belongs to the IPP isomerase type I family and is involved in cholesterol biosynthesis. IDI1 is a peroxisomally-localized enzyme which catalyzes the interconversion of isopentenyl diphosphate（IPP) to its highly electrophilic isomer， dimethylallyl diphosphate（DMAPP)， which is the substrate for the sequential reaction that results in the synthesis of farnesyl diphosphate and， eventually， cholesterol. Peroxisomal deficiency diseases such as Zellweger syndrome and neonatal adrenoleukodystrophy show a reduction in IPP isomerase activity.
