1 research outputs found
Isotopologue Profiling of Triterpene Formation under Physiological Conditions. Biosynthesis of Lupeol-3-(3′‑<i>R</i>‑hydroxy)-stearate in <i>Pentalinon andrieuxii</i>
The
biosynthesis of lupeol-3-(3′<i>R</i>-hydroxy)-stearate
(procrim b, <b>1</b>) was investigated in the Mexican medicinal
plant <i>Pentalinon andrieuxii</i> by <sup>13</sup>CO<sub>2</sub> pulse-chase experiments. NMR analyses revealed positional
enrichments of <sup>13</sup>C<sub>2</sub>-isotopologues in both the
triterpenoid and the hydroxystearate moieties of <b>1</b>. Five
of the six isoprene units reflected a pattern with [1,2-<sup>13</sup>C<sub>2</sub>]- and [3,5-<sup>13</sup>C<sub>2</sub>]-isotopologues
from the respective C<sub>5</sub>-precursors, IPP and DMAPP, whereas
one isoprene unit in the ring E of <b>1</b> showed only the
[3,5-<sup>13</sup>C<sub>2</sub>]-connectivity of the original C<sub>5</sub>-precursor, due to rearrangement of the dammarenyl cation
intermediate during the cyclization process. The presence of <sup>13</sup>C<sub>2</sub>-isotopologues was indicative of [<sup>13</sup>C<sub>2</sub>]acetyl-CoA being the precursor units in the formation
of the fatty acid moiety and of the triterpene via the mevalonate
route. The observed labeling pattern was in agreement with a chair-chair-chair-boat
conformation of the (<i>S</i>)-2,3-oxidosqualene precursor
during the cyclization process, suggesting that the lupeol synthase
from <i>P. andrieuxii</i> is of the same type as that from <i>Olea europea</i> and <i>Taraxacum officinale</i>,
but different from that of <i>Arabidopsis thaliana</i>.
The study shows that <sup>13</sup>CO<sub>2</sub> pulse-chase experiments
are powerful in elucidating, under <i>in vivo</i> conditions
and in a single experiment, the biosynthesis of complex plant products
including higher terpenes