Isoprenoid enzyme systems of silkworm. I. Partial purification of isopentenyl pyrophosphate isomerase, farnesyl pyrophosphate synthetase, and geranylgeranyl pyrophosphate synthetase.

Isopentenyl pyrophosphate isomerase, farnesyl pyrophosphate synthetase, and geranylgeranyl pyrophosphate synthetase were detected in cell-free extracts of Bombyx mori and were partially purified by hydroxyapatite and Sephadex G-100 chromatography. Two forms of farnesyl pyrophosphate synthetase were chromatographically separated. They were designated as farnesyl pyrophosphate synthetases I and II in the order of their elution from hydroxyapatite. Both enzymes catalyzed the exclusive formation of (E,E)-farnesyl pyrophosphate from isopentenyl pyrophosphate and either dimethylallyl pyrophosphate or geranyl pyrophosphate. However, they were not interconvertible, unlike the enzyme from pig liver. These two enzymes resembled each other in pH optima and molecular weights but differed in susceptibility to metal ions. Farnesyl pyrophosphate synthetase II was stimulated by Triton X-100 while synthetase I was inhibited by the same reagent.