Biosynthesis of the Diterpene Phytoalexin Casbene: Partial Purification and Characterization of Casbene Synthetase from Ricinis communis

Casbene synthetase from 67-hour seedlings of Ricinis communis L. which had been treated with Rhizopus stolonifer spores was purified 700-fold by a combination of ammonium sulfate fractionation, QAE A-50 Sephadex chromatography, and G-100 Sephadex chromatography. Polyacrylamide disc gel electrophoresis revealed that the purified fraction was heterogeneous. No casbene synthetase was detected in extracts of seedlings which had not been exposed to the fungal spores; maximum activity was obtained from seedlings 14 hours after exposure to spores.