Isotopologue Profiling of Triterpene Formation under Physiological Conditions. Biosynthesis of Lupeol-3-(3′‑R‑hydroxy)-stearate in Pentalinon andrieuxii

• Published in: Journal of organic chemistry 2014-04, Vol.79 (7), p.2864-2873
• Main Authors: Peña-Rodríguez, Luis M, Yam-Puc, Alejandro, Knispel, Nihat, Schramek, Nicholas, Huber, Claudia, Graßberger, Christoph, Ramírez-Torres, Fabiola G, Escalante-Erosa, Fabiola, García-Sosa, Karlina, Hiebert-Giesbrecht, Mickel R, Chan-Bacab, Manuel J, Godoy-Hernández, Gregorio, Bacher, Adelbert, Eisenreich, Wolfgang
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Carbon Isotopes - chemistry; Cyclization; Intramolecular Transferases - chemistry; Magnetic Resonance Spectroscopy; Olea - chemistry; Pentacyclic Triterpenes - biosynthesis; Pentacyclic Triterpenes - chemical synthesis; Pentacyclic Triterpenes - chemistry; Squalene - analogs & derivatives; Squalene - chemical synthesis; Squalene - chemistry; Stearates - chemical synthesis; Stearates - chemistry; Taraxacum - chemistry; Triterpenes - chemical synthesis; Triterpenes - chemistry
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo402677w

The biosynthesis of lupeol-3-(3′R-hydroxy)-stearate (procrim b, 1) was investigated in the Mexican medicinal plant Pentalinon andrieuxii by 13CO2 pulse-chase experiments. NMR analyses revealed positional enrichments of 13C2-isotopologues in both the triterpenoid and the hydroxystearate moieties of 1. Five of the six isoprene units reflected a pattern with [1,2-13C2]- and [3,5-13C2]-isotopologues from the respective C5-precursors, IPP and DMAPP, whereas one isoprene unit in the ring E of 1 showed only the [3,5-13C2]-connectivity of the original C5-precursor, due to rearrangement of the dammarenyl cation intermediate during the cyclization process. The presence of 13C2-isotopologues was indicative of [13C2]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 (S)-2,3-oxidosqualene precursor during the cyclization process, suggesting that the lupeol synthase from P. andrieuxii is of the same type as that from Olea europea and Taraxacum officinale, but different from that of Arabidopsis thaliana. The study shows that 13CO2 pulse-chase experiments are powerful in elucidating, under in vivo conditions and in a single experiment, the biosynthesis of complex plant products including higher terpenes.