P-amyrin synthase

Characterization of P-Amyrin Synthase from Avena strigosa - A Novel... 

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.

Genetic analysis indicates that two of the 10 sad mutants of A. strigosa that we isolated represent different mutant alleles at the Sadi locus.6 These mutants accumulate radiolabelled 2,3-oxidosqualene but not p-amyrin when the roots are fed with 14C-labelled precursor mevalonic acid, suggesting that the triterpenoid pathway is blocked between 2,3-oxidosqualene and P-amyrin.34 The roots of these mutants also lack detectable P-amyrin synthase activity, but, like the wild type and the other mutants, are unimpaired in cycloartenol synthase (CS) activity and sterol biosynthesis.34 The transcript levels for AsbASl are substantially reduced in roots of sadl mutants, while AsCSl transcript levels are unaffected,35 suggesting that the sadl mutants are either mutated in the AsbASl gene itself or in a gene involved in its regulation. 

KUSHIRO, T., SHIBUYA, M., EBIZUKA, Y P-Amyrin synthase. Cloning of oxidosqualene cyclase that catalyzes the formation of the most popular triterpene among higher plants, Eur. J. Biochem., 1998,256,238-244. 

JPP) and dimethylallyl pyrophosphate (DMAPP) were SQE squalene epoxidase, bAS P-amyrin synthase, oAS... 

HAYASHI, H., HUANG, P.Y., KIRAKOSYAN, A..INOUE, K., HIRAOKA, N., KESHIRO, Y., KUSHIRO, T., SHIBUYA, M EBIZUKA, Y., Cloning and characterization of a cDNA encoding beta-amyrin synthase involved in glycyrrhizin and soyasaponin biosynthesis in licorice, Biol. Pharm. Bull, 2001, 24,912-916. 

Kushiro T, Shibuya M, Ebizuka Y (1998) Molecular cloning of oxidosqualene cyclase cDNA from Panax ginseng the isogene that encodes /3-amyrin synthase. In Ageta H, Aimi N, Ebizuka Y, Pujita T, Honda G (eds) Towards natural medicine research in the 21 st century. Elsevier Science, Amsterdam, p 421... 

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