IDI2, a second isopentenyl diphosphate isomerase in mammals

Abstract

We recently described the identification of a novel isopentenyl diphosphate isomerase, IDI2 in humans and mice. Our current data indicate that, in humans, IDI2 is expressed only in skeletal muscle. Expression constructs of human IDI2 in Saccharomyces cerevisiae can complement isomerase function in an idi1-deficient yeast strain. Furthermore, IDI2 has the ability to catalyze the isomerization of [14C]IPP to [14C]DMAPP. Enzyme kinetic analysis of partially purified IDI2 demonstrate the novel isozyme has a maximal relative specific activity of 1.2 × 10-1 ± 0.3 μmol min-1 mg-1 at pH8.0 with aKmIPP value of 22.8 μM IPP. Both isozymes, IDI1 and IDI2 are localized to the peroxisome by a PTS1-dependent pathway. Finally, our data suggest that IDI2 is regulated independently from IDI1, by a mechanism that may involve PPARα. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.