Smith Mark A, Moon Hangsik, Chowrira Gangamma, Kunst Ljerka
Department of Botany, University of British Columbia, Vancouver, Canada.
Planta. 2003 Jul;217(3):507-16. doi: 10.1007/s00425-003-1015-6. Epub 2003 Mar 18.
Expression of a cDNA encoding the castor bean ( Ricinus communis L.) oleate Delta12-hydroxylase in the developing seeds of Arabidopsis thaliana (L.) Heynh. results in the synthesis of four novel hydroxy fatty acids. These have been previously identified as ricinoleic acid (12-hydroxy-octadec- cis-9-enoic acid: 18:1-OH), densipolic acid (12-hydroxy-octadec- cis-9,15-enoic acid: 18:2-OH), lesquerolic acid (14-hydroxy-eicos- cis-11-enoic acid: 20:1-OH) and auricolic acid (14-hydroxy-eicos- cis-11,17-enoic acid: 20:2-OH). Using mutant lines of Arabidopsis that lack the activity of the FAE1 condensing enzyme or FAD3 ER Delta-15-desaturase, we have shown that these enzymes are required for the synthesis of C20 hydroxy fatty acids and polyunsaturated hydroxy fatty acids, respectively. Analysis of the seed fatty acid composition of transformed plants demonstrated a dramatic increase in oleic acid (18:1) levels and a decrease in linoleic acid (18:2) content correlating to the levels of hydroxy fatty acid present in the seed. Plants in which FAD2 (ER Delta12-desaturase) activity was absent showed a decrease in 18:1 content and a slight increase in 18:2 levels corresponding to hydroxy fatty acid content. Expression of the castor hydroxylase protein in yeast indicates that this enzyme has a low level of fatty acid Delta12-desaturase activity. Lipase catalysed 1,3-specific lipolysis of triacylglycerol from transformed plants demonstrated that ricinoleic acid is not excluded from the sn-2 position of triacylglycerol, but is the only hydroxy fatty acid present at this position.
蓖麻（Ricinus communis L.）油酸Δ12 - 羟化酶编码cDNA在拟南芥（Arabidopsis thaliana (L.) Heynh.）发育种子中的表达导致了四种新型羟基脂肪酸的合成。这些脂肪酸先前已被鉴定为蓖麻油酸（12 - 羟基 - 十八碳 - 顺 - 9 - 烯酸：18:1 - OH）、致密波酸（12 - 羟基 - 十八碳 - 顺 - 9,15 - 烯酸：18:2 - OH）、莱斯奎尔酸（14 - 羟基 - 二十碳 - 顺 - 11 - 烯酸：20:1 - OH）和金盏花酸（14 - 羟基 - 二十碳 - 顺 - 11,17 - 烯酸：20:2 - OH）。利用缺乏FAE1缩合酶或FAD3内质网Δ - 15 - 去饱和酶活性的拟南芥突变株系，我们已经表明这些酶分别是合成C20羟基脂肪酸和多不饱和羟基脂肪酸所必需的。对转基因植物种子脂肪酸组成的分析表明，油酸（18:1）水平显著增加，亚油酸（18:2）含量降低，这与种子中存在的羟基脂肪酸水平相关。缺乏FAD2（内质网Δ12 - 去饱和酶）活性的植物显示18:1含量降低，18:2水平略有增加，这与羟基脂肪酸含量相对应。蓖麻羟化酶蛋白在酵母中的表达表明该酶具有低水平的脂肪酸Δ12 - 去饱和酶活性。脂肪酶催化的转基因植物三酰甘油的1,3 - 特异性脂解表明，蓖麻油酸并不排除在三酰甘油的sn - 2位置，而是该位置存在的唯一羟基脂肪酸。
