This cytosolic sesquiterpenoid synthase requires a divalent cation cofactor (Mg2+ or, to a lesser extent, Mn2+) to neutralize the negative charge of the diphosphate leaving group. While unlikely to encounter geranyl diphosphate (GDP) in vivo as it is localized to plastids, the enzyme can use GDP as a substrate in vitro to produce (+)-(4R)-limonene [cf. EC 188.8.131.52, (R)-limonene synthase]. The enzyme is induced as part of a defense mechanism in the grand fir Abies grandis as a response to stem wounding.
Bohlmann, J., Crock, J., Jetter, R. and Croteau, R. Terpenoid-based defenses in conifers: cDNA cloning, characterization, and functional expression of wound-inducible (E)-α-bisabolene synthase from grand fir (Abies grandis). Proc. Natl. Acad. Sci. USA95 (1998) 6756–6761. [DOI] [PMID: 9618485]