Sitosterol biosynthesis in Hordeum vulgare |
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Authors: | John R Lenton L John Goad Trevor W Goodwin |
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Institution: | Department of Biochemistry, The University, P.O. Box 147, Liverpool, L69 3BX, England |
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Abstract: | Excised barley embryos cultured on a nutrient medium containing methionine-CD3] incorporated deuterium into the newly biosynthesized sterols. Two deuterium atoms were present in 24-methylenecycloartanol, 24-methylenelophenol and campesterol and a maximum of four deuterium atoms were incorporated into 24-ethylidenelophenol, stigmasterol and sitosterol. Mevalonic acid-2-14C(4R)4-3H1] was utilized by the barley embryos to give 28-isofucosterol with a 3H-14C atomic ratio of 3:5 and stigmasterol and sitosterol with a 3H-14C atomic ratio of 2:5. 24-Methylenelophenol and 24-ethylidenelophenol were isolated from barley seed and 24-ethylidenelophenol-2,4-3H3] was incorporated into sitosterol by barley seedlings. These results show that in the production of sitosterol a 24-ethylidenesterol intermediate is produced and it is suggested that this is isomerized to give a Δ24,(25) sterol prior to reduction to the saturated C29 sterol side chain. |
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Keywords: | Gramineae barley biosynthesis side chain alkylation mechanism phytosterols sitosterol stigmasterol 28-isofucosterol |
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