Charakterisierung einer Δ8-Sphingolipid-Desaturase aus Höheren Pflanzen: stereochemische und mechanistische Analyse zum Ursprung vonE/Z-Isomeren

Bioorganic Chemistry of Ceramide

“…A Δ 8 ‐sphingolipid desaturase of higher plants is one of the desaturases that yield a mixture of ( E )‐ and ( Z )‐olefins by syn elimination of two vicinal hydrogen atoms. Stereospecifically dideuterated palmitic acids have been synthesised70 and biosynthetically incorporated into sphingolipids of a transgenic yeast strain, whose fatty acid biosynthesis was inhibited by cerulenin 71. Ceramide 9 has been used to obtain mechanistic information on the reaction catalysed by this desaturase.…”

“…Since each C−H bond cleavage, leading to either the ( E ) or the ( Z ) isomer, occurs at different methylene groups, a common intermediate (radical) can be excluded. It seems that the Δ 8 ‐sphingolipid desaturase is able to convert two different substrate conformations, anti and gauche, independently from each other into the ( E )‐ or ( Z )‐olefin 71…”