title: Type-2 isopentenyl diphosphate isomerase: evidence for a stepwise mechanism.
abstract: 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.
authors: Department of Chemistry, University of Utah, 315 South 1400 East RM 2020, Salt Lake City, Utah 84112, USA.
authors: Nicole A
authors: NA
authors: Heaps
authors: C Dale
authors: CD
authors: Poulter
mesh_terms: D055162:Biocatalysis; D019748:Carbon-Carbon Double Bond Isomerases / Q000378:metabolism*; D045782:Hemiterpenes / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism*; D016963:Thermus thermophilus / Q000201:enzymology
chemical_list: D045782:Hemiterpenes; D009943:Organophosphorus Compounds; C004809:isopentenyl pyrophosphate; C043060:3,3-dimethylallyl pyrophosphate; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase