7-OXO-24ξ(28)-DIHYDROCYCLOEUCALENOL, A POTENT INHIBITOR OF PLANT STEROL BIOSYNTHESIS

Article abstract of DOI:10.1016/0031-9422(82)83024-0

Cycloeucalenol-obtusifoliol isomerase from higher plant cells catalyses the opening of the cyclopropane ring of cycloeucalenol yielding obtusifoliol. 7-Oxo-24ξ(28)-dihydrocycloeucalenol was not a substrate but behaved like a potent inhibitor of the isomerase.The inhibition was reversible and highly specific; the inhibitor needed the presence of the 7-oxo group, the cyclopropane ring and the absence of a 4β-methyl group to be active.Other enzymes involved in plant sterol biosynthesis such as 2,3-oxidosqualene-cycloartenol cyclase and S-adenosyl methionine cycloartenol C-24 methyltransferase were not inhbited by 7-oxo-24ξ(28)-dihydrocycloeucalenol.In vivo treatment of a suspension of bramble cells growing in a liquid medium with 7-oxo-24ξ(28)-dihydrocycloeucalenol resulted in a strong accumulation of 9β,19-cyclopropyl sterols confirming that the main cellular target of the inhibitor is the cycloeucalenol-obtusfoliol isomerase.Key Word Index - Zea mays; Gramineae; Rubus fruticosus; Rosaceae; plant sterol biosynthesis inhibitors; cycloeucalenol-obtusifoliol isomerase; 7-oxo-24ξ(28)-dihydrocycloeucalenol; cellular and enzymatic targets at 7-oxo-24ξ(28)-dihydrocycloeucalenol.