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Updated: May 28, 2026

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity
Published on: October 8, 2018
Type-2 isopentenyl diphosphate isomerase: evidence for a stepwise mechanism
Nicole A Heaps1, C Dale Poulter
1Department of Chemistry, University of Utah, 315 South 1400 East RM 2020, Salt Lake City, Utah 84112, USA.
None:
Isopentenyl diphosphate isomerase (IDI) catalyzes the interconversion of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). These two molecules are the building blocks for construction of isoprenoid carbon skeletons in nature. Two structurally unrelated forms of IDI are known. A variety of studies support a proton addition/proton elimination mechanism for both enzymes. During studies with Thermus thermophilus IDI-2, we discovered that the olefinic hydrogens of a vinyl thiomethyl analogue of isopentenyl diphosphate exchanged with solvent when the enzyme was incubated with D(2)O without concomitant isomerization of the double bond. These results suggest that the enzyme-catalyzed isomerization reaction is not concerted.
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