Zinc Is an Essential Cofactor for Type I Isopentenyl Diphosphate:Dimethylallyl Diphosphate Isomerase

Abstract

Isopentenyl diphosphate (IPP) isomerase catalyzes the interconversion of IPP and dimethylallyl diphosphate (DMAPP). This is an essential reaction in the mevalonate pathway for biosynthesis of isoprenoid compounds. A crystal structure of Escherichia coli type I IPP isomerase shows a his3glu2 octahedral metal binding site (Durbecq, V. et al. EMBO, 2001, 20, 1530-1537). A metal ion analysis of recombinant E. coli type I IPP isomerase purified from metal-free buffer or buffer containing 10 muM ZnCl2 and 10 muM MnCl2 indicated that the protein contained one atom of Zn2+ per molecule. The metal content and the activity of the enzyme did not change when dialyzed for 6 h against metal-free buffer but rapidly decreased upon dialysis against buffer containing o-phenanthroline. Structural and catalytic roles for Zn2+ are discussed.