The alternative pathway C₂₀ Δ8-desaturase from the non-photosynthetic organism Acanthamoeba castellanii is an atypical cytochrome b₅-fusion desaturase

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• 作者：Olga Sayanova ; Richard Haslam ; Baoxiu Qi ; Colin M. Lazarus and Johnathan A. Napier
• 关键词：Alternative pathway ; Cytochrome b₅ ; Desaturase ; Long chain ; Polyunsaturated fatty acids ; Acanthamoeba castellanii
• 刊名：FEBS Letters
• 出版年：2006
• 出版时间：3 April 2006
• 年：2006
• 卷：580
• 期：8
• 页码：1946-1952
• 全文大小：591 K

文摘

A cDNA encoding a C₂₀ Δ8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C₂₀ Δ8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Δ8-desaturase with the Isochrysis galbana Δ9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the alternative pathway for C₂₀ polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C₂₀ fatty acids in the acyl-CoA pool. This is the first report of an alternative pathway C₂₀ Δ8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b₅ domain.