Geraniol synthase

Geraniol synthase converts geranyl diphosphate and water into geraniol and diphosphate. The accepted IUBMB name is geranyl diphosphate diphosphatase, EC 3.1.7.11. That classification describes the overall reaction; it does not on its own identify every bond-breaking step in the mechanism.^[ref]

In a 2004 study, Yoko Iijima and colleagues purified activity from sweet-basil leaf glands. The plant enzyme produced geraniol from geranyl diphosphate, and expression of the identified gene yielded a catalyst with similar activity.^[ref]

The key mechanistic test supplied water containing oxygen-18. Label appeared in geraniol, supporting a route in which cleavage produces a geranyl cation that is captured by water. Merely observing unlabelled geraniol would not distinguish this from a route retaining the substrate's original alcohol oxygen.^[ref]

An ideal isolated conversion of $2\mu \mathrm{mol}$ substrate produces two micromoles each of geraniol and diphosphate. Product amount checks stoichiometry, while isotope labelling tests atom origin. These measurements answer different questions, even when both support the same net reaction. The synthase name should not be read as implying that ATP is required by this specific conversion.