Methylbutenol

Methylbutenol--the isoprene of the West? 

Recently, NOAA and NCAR scientists in Boulder have discovered that an analog of isoprene, methylbutenol (2-methyl-3-buten-2-ol) is released from lodgepole pine forests west of the city.  In collaboration with NCAR scientists we have shown that western U.S. ponderosa and lodgepole pine forests are a major source of this reactive VOC; methylbutenol emissions exceed isoprene emissions in these forests.  We have now established that methylbutenol formation in pine needles is catalyzed by an enzyme we call methylbutenol synthase.  As shown in the scheme below, the methylbutenol synthase reaction appears to be analagous to that catalyzed by isoprene synthase, and enzyme we characterized earlier.  Both enzymes utilize dimethylallyl diphosphate (DMAPP) as the substrate, and probably utilize carbocation mechanisms as shown.  The molecular properties of methylbutenol synthase are under investigation.
 
 

References.  G.M. Silver and R. Fall (1995) Characterization of aspen leaf isoprene synthase, an enzyme responsible for leaf isoprene emission to the atmosphere.  J. Biol. Chem. 270, 13010-13016.  M.C. Wildermuth and R. Fall (1998) Biochemical characterization of stromal and thylakoid-bound isoforms of isoprene synthase in willow leaves. Plant Physiol. 116, 1111-1123.  B. Baker, A. Guenther, J. Greenberg, A. Goldstein, and R. Fall (1999) Canopy fluxes of 2-methyl-3-buten-2-ol over a ponderosa pine forest by relaxed eddy accumulation: Field data and model comparison. J. Geophys. Res. 104, 261107-26114.  A. Fisher, B. Baker, J. Greenberg, and R. Fall (2000) Demonstration of a DMAPP-dependent methylbutenol synthase in pine needles.  In preparation.
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