Enzymatic synthesis of methylbutenol from dimethylallyl diphosphate in needles of Pinus sabiniana

Methylbutenol (2-methyl-3-buten-2-ol) is an abundant volatile organic compo und released from Western U.S. pines. To understand the mechanism of methyl butenol formation, we developed a sensitive gas chromatographic assay for i ts detection and determined that needles of gray pine (Pinus sabiniana) con tain an enzyme that catalyzes the synthesis of methylbutenol from dimethyla llyl diphosphate (DMAPP). The methylbutenol synthase activity was partially purified; its pH optimum was 7-8, and, like other prenyl diphosphate utili zing enzymes, it was dependent on the presence of a divalent cation, prefer ably Mn2+. The enzyme also required K+ or NH4+ for activity. The K-m values for DMAPP and Mn2+ were about 4.8 and 6 mM, respectively. Geranyl diphosph ate was not a substrate for the enzyme, so it is distinct from linalool syn thase, a plant enzyme that catalyzes an analogous reaction. The methylbuten ol synthase reaction may be responsible for the majority of light-dependent methylbutenol production by many pine species in the Western United States . (C) 2000 Academic Press.