I'm teaching the citric acid cycle section of a metabolic
biochemistry course for a colleague and as I was preparing the
lectures, I came across something that made me curious. I can only
hope the students will be too, so I thought I'd pose the question to
plant ed. (After all, anything I share about what makes plants
specially with a group of pre-med students is always welcome). this
may be rather elementary, but I don't know the answer.
Several Biochem texts (Stryer, Voet & Voet, Mathews & van Holde)
mention fluoroacetate, "one of the most toxic small molecules known".
Fluoroacetate "occurs in the leaves of certain African, Australian
and South American poisonous plants" and is converted via acetate
thiokinase to fluoroacetyl-CoA, and then by citrate synthase to
fluorocitrate, which inhibits aconitase and accounts for a high
portion of the toxicity.
My question is, why doesn't this compound poison the plants? I know
plants have citrate synthase. My search of the Arabidopsis ESTs for
acetate thiokinase came up empty, but that doesn't necessarily mean
it's not there. Does anyone know if this enzyme occurs in plants?
If it doesn't, is this what allows the plants to make this compound?
If it does, how does the plant keep from poisoning it's own TCA
cycle? Sequestration?
Any insight welcome!
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Julia Frugoli
Asst. Professor
Biological Sciences
Clemson University
132 Long Hall
Clemson, SC 29634
PHONE (864) 656-1859
FAX (864) 656-0435
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