PLANT PHYSIOLOGY , Vol 112, Issue 1 171-182, Copyright © 1996 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Light-Dependent Isoprene Emission (Characterization of a Thylakoid-Bound Isoprene Synthase in Salix discolor Chloroplasts)
M. C. Wildermuth and R. Fall
Department of Chemistry and Biochemistry, and the Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309-0215
Isoprene synthase is an enzyme that is responsible for the production of
the volatile C5 hydrocarbon, isoprene, in plant leaves. Isoprene formation
in numerous C3 plants is interesting because (a) large quantities of
isoprene are emitted, 5 x 1014 g of C annually, (b) a plant may release 1
to 8% of its fixed C as isoprene, and (c) the function of plant isoprene
production is unknown. Because of the dependence of foliar isoprene
emission on light, the existence of a plastidic isoprene synthase has been
postulated. To pursue this idea, a method to isolate chloroplasts from
Salix discolor was developed and shows a plastidic isoprene synthase that
is tightly bound to the thylakoid membrane and accessible to trypsin
inactivation. The thylakoid-bound isoprene synthase has catalytic
properties similar to known soluble isoprene synthases; however, the
relationship between these enzymes is unknown. The discovery of a
thylakoid-bound isoprene synthase with a stromal-facing domain places it in
the chloroplast, where it may be subject to numerous direct and indirect
light-mediated effects. Implications for the light-dependent regulation of
foliar isoprene production and its function are presented.
