Geranylgeranyl-diphosphate:isopentenyl-diphosphate transtransferase

Geranylgeranyl-diphosphate:isopentenyl-diphosphate transtransferase may refer to:
 * Geranylfarnesyl diphosphate synthase, enzyme
 * Hexaprenyl diphosphate synthase (geranylgeranyl-diphosphate specific), enzyme
 * All-trans-nonaprenyl diphosphate synthase (geranylgeranyl-diphosphate specific), enzyme