Proton exchange in type II isopentenyl diphosphate isomerase.

Type II isopentenyl diphosphate:dimethylallyl diphosphate (IPP:DMAPP) isomerase from Synechocystis PCC 6803 catalyzes the interconversion of IPP and DMAPP. Upon incubation of the enzyme with IPP or DMAPP in (H2O)-H-2, one deuterium is incorporated into the C2 methylene of IPP, two deuteriums are incorporated at C4, and three deuteriums are incorporated into the (E)-methyl of DMAPP.