Hexaprenyl diphosphate synthase ((2E,6E) farnesyl diphosphate specific)

Hexaprenyl-diphosphate synthase ((2E,6E)-farnesyl-diphosphate specific) (EC 2.5.1.83, HexPS, hexaprenyl pyrophosphate synthetase, hexaprenyl diphosphate synthase) is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate:isopentenyl-diphosphate farnesyltranstransferase (adding 3 isopentenyl units). This enzyme catalyses the following chemical reaction

(2E,6E)-farnesyl diphosphate + 3 isopentenyl diphosphate ⇌ 3 diphosphate + all-trans-hexaprenyl diphosphate

The enzyme prefers farnesyl diphosphate to geranylgeranyl diphosphate as an allylic substrate.