Abstract
Type 2 isopentenyl diphosphate isomerase is a flavoenzyme that catalyzes interconversion between isopentenyl diphosphate and dimethylallyl diphosphate, which are precursors for the biosynthesis of diverse isoprenoid compounds. The reaction mechanism of the enzyme, which requires redox coenzymes FMN and NAD(P)H for activity, attracts interest because the enzyme catalyzes isomerization, a reaction without net redox change. From our studies using type 2 isopentenyl diphosphate isomerase from a thermoacidophilic archaeon Sulfolobus shibatae, consumption of only a catalytic amount of NAD(P)H and actual requirement for reduced FMN as a coenzyme were shown. Moreover, our structural and mutagenic works on the enzyme, together with enzymological studies by other groups, revealed the unique function of the flavin coenzyme as a general acid-base catalyst without redox role.
