Isoprene


The isoprene puzzles

  For several years we have been working to understand the biochemical mechanism and
regulation of isoprene formation in leaves of green plants.  Underlying this work are many
puzzling questions. Why is isoprene formed? Why do some, but not all, plants produce this hydrocarbon? Why is isoprene only formed in fully expanded, not immature, leaves?

In the course of our work, while attempting to clone the isoprene synthase gene from plants,
we accidentally discovered that bacteria in the Bacillusfamily produce isoprene.  In addition,
B. subtilisexhibits a remarkable pattern of three peaks of isoprene formation during growth, as shown in the figure below.  We hypothesize that these peaks may represent the operation of a "safety valve," where excess isoprenoid carbon is released from the cell; alternatively, isoprene
may be a metabolic signal molecule related to repression of stationary phase genes.  On-going research in the B. subtilissystem is taking advantage of genomic, molecular, and biochemical approaches to testing these models.

References. W.P. Wagner, M. Nemecek-Marshall, and R. Fall (1999) Three distinct phases
of isoprene formation during the growth and sporulation of Bacillus subtilis.  J. Bacteriol. 181,
4700-4703.  W.P. Wagner, D. Helmig, and R. Fall (2000) Isoprene biosynthesis in Bacillus subtilisvia the methylerythritol phosphate pathway.  J. Nat. Prod. 63, 37-40.  R. Fall and S. D. Copley (2000) Minireview: Bacterial sources and sinks of isoprene, a reactive atmospheric hydrocarbon. Environ. Microbiol., in press.

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