2.3- oxidosqualene:cycloartenol cyclase

In plants, sterols arise through the intermediacy of cycloartenol (3) and 2,3-oxidosqualene cycloartenol cyclase (EC 5.4.99.8), whereas, in animals, sterols arise from lanost-erol (15) and 2,3-oxidosqualene lanosterol cyclase (EC 5.4.99.7) (Figs. 23.7 and 23.8). Despite several reports (all... 

Squalene monooxygenase (2,3-epoxydizing) 2 2,3-oxidosqualene cyclase (e.g., 2,3-oxido-squalene lanosterol cyclase and 2,3-oxidosqualene cycloartenol cyclase)... 

Purification. The first development is the purification, to apparent homogeneity, of several cyclase enzymes from natural sources. Abe, Ebizuka and coworkers worked out methods for the purification of oxidosqualene-p-amyrin and oxidosqualene-cycloartenol cyclases from Piswn sativum and Rabdosia Japonica, and of oxidosqualene-lanosterol cyclase from rat liver (31-34). These purification... 

HENRY, M., RAHIER, A., TATON, M., Effect of gypsogenin 3,0-glucuronide pretreatment of Gypsophila paniculata and Saponaria officinalis cell suspension cultures on the activities of microsomal 2,3-oxidosqualene cycloartenol and amyrin cyclases, Phytochemistry, 1992,31,3855-3859. 

TATON, M., BENVENISTE, P., RAHIER, A., N-[(l,5,9)-tnmethyl-decyl]-4a,10-dimethyl-8-aza-trans-decal-3P-ol A novel potent inhibitor of 2,3-oxidosqualene cycloartenol and lanosterol cyclases, Biochem. Biophys. Res. Comm., 1986, 138, 764-770. 

Fig. 5.1 Cyclization of 2,3-oxidosqualene to sterols and triterpenoids. The 2,3-oxidosqualene cyclase enzymes that catalyse the formation of the different products are indicated LS, lanosterol synthase CS, cycloartenol synthase LuS, lupeol synthase PAS, P-amyrin synthase aAS, a-amyrin synthase.

FANG, T-Y., BAISTED, D.J., 2,3-Oxidosqualene cyclase and cycloartenol-S-adenosylmethionine methyltransferase activitites in vivo in the cotyledon and axis tissues of germinating pea seeds, Biochem. J., 1975,150, 323-328. 

A comparison of the efficiency of the 2,3-oxidosqualene cyclase from human placenta microsomes with that from rat liver microsomes has led to the conclusion that in human placenta the conversion of squalene into lanosterol is limited by the rate of squalene epoxidation. Tracer from [l- C]-2,3-oxidosqualene was incorporated into cycloartenol (1% yield) by a cell-free system from Alnus glutinosa but none of the triterpenoid glutinone was synthesized from the labelled precursor. When 2,3-oxidosqualene was incubated with cell-free extracts from corn embryos the only product was cycloartenol, whereas when l-trarts-T-nor-2,3-oxidosqualene (9) was the substrate both 31-norcycloartenol and 31-norlanosterol were formed " l-c/s-T-nor-2,3-oxidosqualene (10) gave rise to no detectable cyclization products... 

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