Studies in phytosterol biosynthesis. Mechanism of biosynthesis of cycloartenol.
1. The mechanism of cycloartenol biosynthesis in leaves of Solanum tuberosum was investigated with the use of [2-(14)C,(4R)-4-(3)H(1)]mevalonic acid. 2. The (3)H/(14)C atomic ratio in cycloartenol was 6:6, the same as that in squalene; this eliminates lanosterol as a possible biosynthetic precursor of cycloartenol, and indicates that a hydrogen migration from C-9 to C-8 occurs. 3. Chemical isomerization of the cycloartenol to lanosterol ((3)H/(14)C ratio 5:6) and parkeol ((3)H/(14)C ratio 6:6) confirms the hydrogen migration from C-9 to C-8. 4. Possible mechanisms for the biosynthesis of cycloartenol and parkeol are discussed. 5. The (3)H/(14)C ratio for 24-methylenecycloartanol was 6:6, demonstrating that the hydrogen atom at C-24 is retained during alkylation of the cycloartenol side chain.
D002247:Carbon Isotopes; D002776:Cholestanes / Q000378:metabolism; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D003521:Cyclopropanes; D008798:Mevalonic Acid / Q000378:metabolism; D008954:Models, Biological; D010944:Plants / Q000378:metabolism*; D012822:Silicon Dioxide; D013185:Squalene / Q000378:metabolism; D013261:Sterols / Q000096:biosynthesis*; D013729:Terpenes / Q000378:metabolism; D014316:Tritium
D002247:Carbon Isotopes; D002776:Cholestanes; D003521:Cyclopropanes; D013261:Sterols; D013729:Terpenes; D014316:Tritium; D012822:Silicon Dioxide; D013185:Squalene; D008798:Mevalonic Acid